func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, m, a[1000005], ans = 0;   inline long long read() {     long long red = 0, f_f = 1;     char ch = getchar();     while (ch >  9  || ch <  0 ) {       if (ch ==  - ) f_f = -1;       ch = getchar();     }     while (ch >=  0  && ch <=  9 ) red = red * 10 + ch -  0 , ch = getchar();     return red * f_f;   }   signed main() {     n = (1ll << read()), m = read();     for (long long i = 0; i < n; i++) a[i] = read(), ans += a[i];     printf( %.6lf n , 1.0 * ans / n);     while (m--) {       long long x = read(), y = read();       ans -= a[x];       a[x] = y;       ans += a[x];       printf( %.6lf n , 1.0 * ans / n);     }     return 0;   }   