func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, m;   long long a[10001], f[10001];   int main() {     int d, x, y;     scanf( %I64d %I64d , &n, &m);     f[0] = f[1] = 1;     for (int i = 2; i <= n; i++) f[i] = f[i - 1] + f[i - 2], f[i] %= 1000000000LL;     for (int i = 1; i <= n; i++) scanf( %I64d , &a[i]);     for (int i = 1; i <= m; i++) {       scanf( %I64d , &d);       if (d == 1) {         scanf( %I64d %I64d , &x, &y);         a[x] = y;       } else {         long long ans = 0;         scanf( %I64d %I64d , &x, &y);         for (int i = x; i <= y; i++) ans += f[i - x] * a[i], ans %= 1000000000LL;         printf( %I64d n , ans);       }     }     return 0;   }   