func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 200000 + 5;   const int mod = 1000000000;   int a[N], f[N];   int main() {     int n, m, type, x, v, l, r, d, sum;     scanf( %d%d , &n, &m);     f[0] = f[1] = 1;     for (int i = 2; i < n; ++i) f[i] = (f[i - 1] + f[i - 2]) % mod;     for (int i = 0; i < n; ++i) scanf( %d , &a[i]);     for (int i = 0; i < m; ++i) {       scanf( %d , &type);       if (type == 1) {         scanf( %d%d , &x, &v);         x--;         a[x] = v;       } else if (type == 2) {         scanf( %d%d , &l, &r);         sum = 0;         r--;         l--;         for (int j = 0; j <= r - l; ++j) {           sum = (sum + (long long)(f[j]) * (long long)(a[l + j])) % mod;         }         cout << sum << endl;       }     }   }   