Approximate

#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());

typedef long long C;
typedef complex<C> P;
#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;

int solve() {
    int n, q; std::cin >> n >> q;
    vector<int> v(n);
    for (int i = 0; i < n; i++) {
        std::cin >> v[i];
    }

    vector<int> prefA(n+1), prefB(n+1);
    for (int i = 0; i < n; i++) {
        prefA[i+1]=prefA[i]+v[i]*v[i];
    }

    for (int i = 0; i < n; i++) {
        prefB[i+1]=prefB[i]+v[i];
    }

    //__print(prefB); std::cout  << std::endl;


    vector<vector<int>> pref(n+1, vector<int>(101));

    for (int i = 0; i < n; i++) {
        pref[i+1]=pref[i];
        pref[i+1][v[i]]++;
    }
    std::cout << fixed << setprecision(6);



    while(q--) {
        int a, b; std::cin >> a >> b;
        a--;

        double A=(prefA[b]-prefA[a]);
        double B=-2*(prefB[b]-prefB[a]);

        double mean=1.0*(prefB[b]-prefB[a])/(b-a);

        //std::cout << A << " " << B << std::endl;
        //std::cout << mean << std::endl;

        std::cout << (A+B*mean+(b-a)*mean*mean)/(b-a) << std::endl;

        continue;

        vector<int> curr=pref[b];
        for (int i = 1; i <= 100; i++) {
            curr[i]-=pref[a][i];
        }
        //__print(curr); std::cout  << std::endl;
        double res=0;
        //double mean=(1.0*prefB[b]-prefB[a])/(b-a);
        //std::cout << "mean: " << mean << std::endl;
        //for (int i = 1; i <= 100; i++) {
            //for (int j = 0; j < curr[i]; j++) {
                //res+=(i-mean)*(i-mean);
            //}
        //}

        std::cout << res/(b-a) << std::endl;
        
    }


    return 0;
    while(q--) {
        int a, b; std::cin >> a >> b;
        a--;
        double A=prefA[b]-prefA[a];
        double B=(prefB[b]-prefB[a]);
        int k=(b-a);
        double mean=(1.0*prefB[b]-prefB[a])/k;
        std::cout << "mean: " << mean << std::endl;

        std::cout << "res: " << A+-2*B*mean+mean*mean << std::endl;

        //std::cout << "-B/2: " << -1.0*B/2 << std::endl;
        //std::cout << "lol: " << (-1.0*B/2+B)*(-1.0*B/2) << std::endl;
        //std::cout << A << " " << B << std::endl;

        //std::cout << mean << std::endl;
        //std::cout << A+B*mean*k+k*mean*mean << 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