func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     long long p = 1000000000;     vector<int> a;     a.resize(n);     long long fib[100];     fib[0] = 1;     fib[1] = 1;     for (long long i = 2; i < 100; i++) fib[i] = (fib[i - 1] + fib[i - 2]) % p;     for (int i = 0; i < n; i++) cin >> a[i];     long long t, x, y;     for (int i = 0; i < m; i++) {       cin >> t >> x >> y;       if (t == 1) {         x--;         a[x] = y;       } else {         x--;         y--;         long long res = 0;         for (long long j = 0; j + x <= y; j++) {           res += a[x + j] * fib[j];           res = res % p;         }         cout << res << endl;       }     }     return 0;   }   