func_code_string: #include <bits/stdc++.h>   namespace solution {}   namespace solution {   class ISolution {    public:     virtual void init(){};     virtual bool input() { return false; };     virtual void output(){};     virtual int run() = 0;   };   }  // namespace solution   namespace solution {   using namespace std;   const long long MOD = 1000000000LL;   const int SIZE = 2 * 100000 + 11;   const int QUERY_SIZE = 2 * 100000 + 11;   int n, m;   long long A[SIZE];   long long F[SIZE];   void query_1() {     int x, v;     cin >> x >> v;     A[x] = v;   }   void query_2() {     int l, r;     cin >> l >> r;     int len = r - l + 1;     long long sum = 0;     for (int i = 0; i < len; ++i) sum = (sum + F[i] * A[l + i]) % MOD;     cout << sum << endl;   }   void solve() {     F[0] = F[1] = 1;     for (int i = 2; i < SIZE; ++i) F[i] = (F[i - 1] + F[i - 2]) % MOD;     for (int i = 0; i < m; ++i) {       int t;       cin >> t;       if (t == 1) {         query_1();       } else if (t == 2) {         query_2();       }     }   }   class Solution : public ISolution {    public:     bool input() {       if (!(cin >> n >> m)) return false;       for (int i = 0; i < n; ++i) cin >> A[i + 1];       return true;     }     int run() {       while (init(), input()) {         solve();         output();       }       return 0;     }   };   }  // namespace solution   int main() { return solution::Solution().run(); }   