func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     int n, r;     cin >> n >> r;     vector<double> a(1 << n);     double sum = 0, div = (double)(1 << n);     for (int i = 0; i < (1 << n); i++) {       int x;       cin >> x;       a[i] = (double)x;       sum += a[i];     }     double ans = sum / div;     cout << setprecision(7) << fixed << ans <<   n ;     while (r--) {       int z, g;       cin >> z >> g;       double gg = (double)g;       sum += (gg - a[z]);       a[z] = gg;       ans = sum / div;       cout << setprecision(7) << fixed << ans <<   n ;     }     return 0;   }   