Monistus

#include <bits/stdc++.h>

#define MODE 1

#if MODE
#define debug(x) cout << #x << ": " << x << endl
#define log(x) cout << x << endl
#define test(x) x
#else
#define debug(x)
#define log(x)
#define test(x)
#endif

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define fi first
#define se second
#define X real()
#define Y imag()

using namespace std;
using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull = unsigned long long;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
using P = complex<ll>;

const ll M = 1000000007; // 998244353

void solve() {
    string s;
    cin >> s;
    
    reverse(all(s));
    
    while (s.size()) {
        char c = s.back();
        s.pop_back();
        if (c >= '1' && c <= '9') s += s.substr(s.size()-c+'0', c-'0');
        else cout << c;
    }
    cout << '\n';
}

int main() {
    cin.tie(0) -> sync_with_stdio(0);

    int t = 1;
    if (t == 0) cin >> t;
    while (t--) solve();

    return 0;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED