func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 19;   int a[1 << N];   int main() {     int n, q;     cin >> n >> q;     long long sum = 0;     for (int i = 0; i < (1 << n); i++) cin >> a[i], sum += a[i];     cout << setprecision(10) << 1.0 * sum / (1 << n) <<   n ;     for (int i = 0; i < q; i++) {       int id, v;       cin >> id >> v;       sum += v - a[id];       a[id] = v;       cout << setprecision(10) << 1.0 * sum / (1 << n) <<   n ;     }   }   