func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e6 + 5;   int C[N];   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     int n, r;     cin >> n >> r;     double sum = 0;     for (int i = 0; i < (1 << n); i++) {       cin >> C[i];       sum += C[i];     }     cout << setprecision(15) << fixed << sum / (1 << n) <<   n ;     while (r--) {       int z, g;       cin >> z >> g;       sum += g - C[z];       C[z] = g;       cout << setprecision(15) << fixed << sum / (1 << n) <<   n ;     }     return 0;   }   