A TIMES B!

input/code.cpp: In function 'int solve()':
input/code.cpp:324:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  324 |     for (int i = 0; i < a.size(); i++) A[i]=a[i]-'0';
      |                     ~~^~~~~~~~~~
input/code.cpp:325:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  325 |     for (int i = 0; i < b.size(); i++) B[i]=b[i]-'0';
      |                     ~~^~~~~~~~~~
input/code.cpp:332:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  332 |     for (int i = 0; i < ab.size()-1; i++) {
      |                     ~~^~~~~~~~~~~~~
input/code.cpp:339:23: warning: comparison of integer expressions of different signedness:...

#ifdef ONPC
    #define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>

#define char unsigned char
#define rep(i, a, b) for(int i=a; i< (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
#define pb push_back

#define LSOne(S) ((S) & -(S))

using namespace std;
// mt19937 rnd(239);
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());

template <typename T> int sgn(T x) { return (T(0) < x) - (x < T(0)); }
typedef long double T;
typedef complex<T> pt;
#define X real()
#define Y imag()

template<class T>
istream& operator>> (istream& is, complex<T>& p) {
    T value;
    is >> value;
    p.real(value);
    is >> value;
    p.imag(value);
    return is;
}

typedef long long ll;
typedef long double ld;

using pi = pair<ll, ll>;
using vi = vector<ll>;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;

int popcnt(int x) { return __builtin_popcount(x); }
int popcnt(ll x) { return __builtin_popcountll(x); }

#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
#define LB(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define UB(c, x) distance((c).begin(), upper_bound(all(c), (x)))

void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef DEBUG
#define dbg(x...) cerr << "\e[91m"<<__func__<<":"<<__LINE__<<" [" << #x << "] = ["; _print(x); cerr << "\e[39m" << endl;
#else
#define dbg(x...)
#endif

template<typename S, typename T = S> void chmin(S &s, T t) {s = s < t ? s : t;}
template<typename S, typename T = S> void chmax(S &s, T t) {s = s > t ? s : t;}

const int INF = 1e9; // 10^9 = 1B is < 2^31-1
const ll LLINF = 4e18; // 4*10^18 is < 2^63-1
const double EPS = 1e-9;
const ll MOD = 1e9+7;

namespace fft {
    struct cmpl {
        double x, y;
        cmpl() {
            x = y = 0;
        }
        cmpl(double x, double y) : x(x), y(y) {}
        inline cmpl conjugated() const {
            return cmpl(x, -y);
        }
    };
    inline cmpl operator+(cmpl a, cmpl b) {
        return cmpl(a.x + b.x, a.y + b.y);
    }
    inline cmpl operator-(cmpl a, cmpl b) {
        return cmpl(a.x - b.x, a.y - b.y);
    }
    inline cmpl operator*(cmpl a, cmpl b) {
        return cmpl(a.x * b.x - a.y * b.y, a.x * b.y + a.y * b.x);
    }

    int base = 1; // current power of two (2^base >= n)
    vector<cmpl> roots = {{0, 0}, {1, 0}}; // complex roots of 1 (with bases from 1 to base), 1-based indexing
    vector<int> rev = {0, 1}; // rev[i] = reversed bit representation of i
    const double PI = static_cast<double>(acosl(-1.0));

    void ensure_base(int nbase) { // if base < nbase increase it
        if (nbase <= base) {
            return;
        }
        rev.resize(1 << nbase);
        for (int i = 1; i < (1 << nbase); i++) {
            rev[i] = (rev[i >> 1] >> 1) + ((i & 1) << (nbase - 1));
        }
        roots.resize(1 << nbase);
        while (base < nbase) {
            double angle = 2 * PI / (1 << (base + 1));
            for (int i = 1 << (base - 1); i < (1 << base); i++) {
                roots[i << 1] = roots[i];
                double angle_i = angle * (2 * i + 1 - (1 << base));
                roots[(i << 1) + 1] = cmpl(cos(angle_i), sin(angle_i));
            }
            base++;
        }
    }

    void fft(vector<cmpl>& a, int n = -1) {
        if (n == -1) {
            n = (int) a.size();
        }
        assert((n & (n - 1)) == 0); // ensure that n is a power of two
        int zeros = __builtin_ctz(n);
        ensure_base(zeros);
        int shift = base - zeros;
        for (int i = 0; i < n; i++) {
            if (i < (rev[i] >> shift)) {
                swap(a[i], a[rev[i] >> shift]);
            }
        }
        for (int k = 1; k < n; k <<= 1) {
            for (int i = 0; i < n; i += 2 * k) {
                for (int j = 0; j < k; j++) {
                    cmpl z = a[i + j + k] * roots[j + k];
                    a[i + j + k] = a[i + j] - z;
                    a[i + j] = a[i + j] + z;
                }
            }
        }
    }

    vector<cmpl> fa, fb;

    vector<long long> square(const vector<int>& a) {
        if (a.empty()) {
            return {};
        }
        int need = (int) a.size() + (int) a.size() - 1;
        int nbase = 1;
        while ((1 << nbase) < need) {
            nbase++;
        }
        ensure_base(nbase);
        int sz = 1 << nbase;
        if ((sz >> 1) > (int) fa.size()) {
            fa.resize(sz >> 1);
        }
        for (int i = 0; i < (sz >> 1); i++) {
            int x = (2 * i < (int) a.size() ? a[2 * i] : 0);
            int y = (2 * i + 1 < (int) a.size() ? a[2 * i + 1] : 0);
            fa[i] = cmpl(x, y);
        }
        fft(fa, sz >> 1);
        cmpl r(1.0 / (sz >> 1), 0.0);
        for (int i = 0; i <= (sz >> 2); i++) {
            int j = ((sz >> 1) - i) & ((sz >> 1) - 1);
            cmpl fe = (fa[i] + fa[j].conjugated()) * cmpl(0.5, 0);
            cmpl fo = (fa[i] - fa[j].conjugated()) * cmpl(0, -0.5);
            cmpl aux = fe * fe + fo * fo * roots[(sz >> 1) + i] * roots[(sz >> 1) + i];
            cmpl tmp = fe * fo;
            fa[i] = r * (aux.conjugated() + cmpl(0, 2) * tmp.conjugated());
            fa[j] = r * (aux + cmpl(0, 2) * tmp);
        }
        fft(fa, sz >> 1);
        vector<long long> res(need);
        for (int i = 0; i < need; i++) {
            res[i] = llround(i % 2 == 0 ? fa[i >> 1].x : fa[i >> 1].y);
        }
        return res;
    }
    
    // interface

    vector<long long> multiply(const vector<int>& a, const vector<int>& b) {
        if (a.empty() || b.empty()) {
            return {};
        }
        if (a == b) {
            return square(a);
        }
        int need = (int) a.size() + (int) b.size() - 1;
        int nbase = 1;
        while ((1 << nbase) < need) nbase++;
        ensure_base(nbase);
        int sz = 1 << nbase;
        if (sz > (int) fa.size()) {
            fa.resize(sz);
        }
        for (int i = 0; i < sz; i++) {
            int x = (i < (int) a.size() ? a[i] : 0);
            int y = (i < (int) b.size() ? b[i] : 0);
            fa[i] = cmpl(x, y);
        }
        fft(fa, sz);
        cmpl r(0, -0.25 / (sz >> 1));
        for (int i = 0; i <= (sz >> 1); i++) {
            int j = (sz - i) & (sz - 1);
            cmpl z = (fa[j] * fa[j] - (fa[i] * fa[i]).conjugated()) * r;
            fa[j] = (fa[i] * fa[i] - (fa[j] * fa[j]).conjugated()) * r;
            fa[i] = z;
        }
        for (int i = 0; i < (sz >> 1); i++) {
            cmpl A0 = (fa[i] + fa[i + (sz >> 1)]) * cmpl(0.5, 0);
            cmpl A1 = (fa[i] - fa[i + (sz >> 1)]) * cmpl(0.5, 0) * roots[(sz >> 1) + i];
            fa[i] = A0 + A1 * cmpl(0, 1);
        }
        fft(fa, sz >> 1);
        vector<long long> res(need);
        for (int i = 0; i < need; i++) {
        res[i] = llround(i % 2 == 0 ? fa[i >> 1].x : fa[i >> 1].y);
        }
        return res;
    }

    vector<int> multiply_mod(const vector<int>& a, const vector<int>& b, int m) {
        if (a.empty() || b.empty()) {
            return {};
        }
        int need = (int) a.size() + (int) b.size() - 1;
        int nbase = 0;
        while ((1 << nbase) < need) {
            nbase++;
        }
        ensure_base(nbase);
        int sz = 1 << nbase;
        if (sz > (int) fa.size()) {
            fa.resize(sz);
        }
        for (int i = 0; i < (int) a.size(); i++) {
            int x = (a[i] % m + m) % m;
            fa[i] = cmpl(x & ((1 << 15) - 1), x >> 15);
        }
        fill(fa.begin() + a.size(), fa.begin() + sz, cmpl{0, 0});
        fft(fa, sz);
        if (sz > (int) fb.size()) {
            fb.resize(sz);
        }
        if (a == b) {
            copy(fa.begin(), fa.begin() + sz, fb.begin());
        } else {
            for (int i = 0; i < (int) b.size(); i++) {
                int x = (b[i] % m + m) % m;
                fb[i] = cmpl(x & ((1 << 15) - 1), x >> 15);
            }
            fill(fb.begin() + b.size(), fb.begin() + sz, cmpl{0, 0});
            fft(fb, sz);
        }
        double ratio = 0.25 / sz;
        cmpl r2(0, -1);
        cmpl r3(ratio, 0);
        cmpl r4(0, -ratio);
        cmpl r5(0, 1);
        for (int i = 0; i <= (sz >> 1); i++) {
            int j = (sz - i) & (sz - 1);
            cmpl a1 = (fa[i] + fa[j].conjugated());
            cmpl a2 = (fa[i] - fa[j].conjugated()) * r2;
            cmpl b1 = (fb[i] + fb[j].conjugated()) * r3;
            cmpl b2 = (fb[i] - fb[j].conjugated()) * r4;
            if (i != j) {
                cmpl c1 = (fa[j] + fa[i].conjugated());
                cmpl c2 = (fa[j] - fa[i].conjugated()) * r2;
                cmpl d1 = (fb[j] + fb[i].conjugated()) * r3;
                cmpl d2 = (fb[j] - fb[i].conjugated()) * r4;
                fa[i] = c1 * d1 + c2 * d2 * r5;
                fb[i] = c1 * d2 + c2 * d1;
            }
            fa[j] = a1 * b1 + a2 * b2 * r5;
            fb[j] = a1 * b2 + a2 * b1;
        }
        fft(fa, sz);
        fft(fb, sz);
        vector<int> res(need);
        for (int i = 0; i < need; i++) {
            long long aa = llround(fa[i].x);
            long long bb = llround(fb[i].x);
            long long cc = llround(fa[i].y);
            res[i] = static_cast<int>((aa + ((bb % m) << 15) + ((cc % m) << 30)) % m);
        }
        return res;
    }
}  // namespace fft
/*
use these:
vector<int> multiply_mod(const vector<int>& a, const vector<int>& b, int m)
vector<ll> square(const vector<int>& a)
vector<ll> multiply(const vector<int>& a, const vector<int>& b) // (if a == b it uses square)
*/

int solve() {
    string a,b;std::cin >> a >> b;
    reverse(all(a));
    reverse(all(b));
    vector<int> A(a.size()), B(b.size());
    for (int i = 0; i < a.size(); i++) A[i]=a[i]-'0';
    for (int i = 0; i < b.size(); i++) B[i]=b[i]-'0';

    vector<ll> ab=fft::multiply(A,B);
    ab.pb(0);


    string res="";
    for (int i = 0; i < ab.size()-1; i++) {
        if(ab[i]>=10) {
            ab[i+1]+=ab[i]/10;
            ab[i]%=10;
        }
    }

    for (int i = 0; i < ab.size(); i++) {
        res+=to_string(ab[i])[0];
    }
    while(!res.empty() && res.back()=='0') res.pop_back();
    reverse(all(res));
    std::cout << res << std::endl;
    
    


    
    return 0;
}

int32_t main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int TET = 1;
    //cin >> TET;
    for (int i = 1; i <= TET; i++) {
        #ifdef ONPC
            cout << "TEST CASE#" << i << endl;
        #endif
        
        if (solve()) {
            break;
        }

        #ifdef ONPC
            cout << "__________________________" << endl;
        #endif
    }
    #ifdef ONPC
        cerr << endl << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl;
    #endif
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: ACCEPTED

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: ACCEPTED

Test 62

Verdict: ACCEPTED

Test 63

Verdict: ACCEPTED

Test 64

Verdict: ACCEPTED

Test 65

Verdict: ACCEPTED