func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void out(T x) {     cout << x << endl;     exit(0);   }   using ll = long long;   using ld = long double;   const int maxn = 1e6 + 5;   int n, r;   ll c[maxn];   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     cout << fixed << setprecision(10);     ll sum = 0;     cin >> n >> r;     for (int i = 0; i < 1 << n; i++) {       cin >> c[i];       sum += c[i];     }     ld res = 1.0 * sum / (1 << n);     cout << res <<   n ;     while (r--) {       int i, g;       cin >> i >> g;       sum -= c[i];       c[i] = g;       sum += c[i];       ld res = 1.0 * sum / (1 << n);       cout << res <<   n ;     }     return 0;   }   