func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     int n, tt;     cin >> n >> tt;     vector<int> a(1 << n);     long long sum = 0;     for (int i = 0; i < (1 << n); i++) {       cin >> a[i];       sum += (long long)a[i];     }     cout << fixed << setprecision(17) << (double)sum / (1 << n) <<   n ;     while (tt--) {       int x, y;       cin >> x >> y;       sum += y - a[x];       a[x] = y;       cout << fixed << setprecision(17) << (double)sum / (1 << n) <<   n ;     }     return 0;   }   