func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MaxN = 123456, Mod = 1000000000;   long long a[MaxN], f[MaxN];   int main(void) {     int i, j, n, m;     f[0] = f[1] = 1;     for (i = 2; i < MaxN; i++) f[i] = (f[i - 1] + f[i - 2]) % Mod;     while (scanf( %d %d , &n, &m) != EOF) {       int i, t, l, r;       for (i = 0; i < n; i++) scanf( %I64d , &a[i]);       for (j = 0; j < m; j++) {         scanf( %d %d %d , &t, &l, &r);         if (t == 1)           a[l - 1] = r;         else {           long long s = 0;           for (i = 0; i <= r - l; i++) s = (s + a[i + l - 1] * f[i]) % Mod;           printf( %d n , (int)s);         }       }     }   }   