func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m;   string s;   string change(string s, int l, int r, char c1, char c2) {     for (int i = l - 1; i < r; i++) {       if (s[i] == c1) {         s[i] = c2;       }     }     return s;   }   int main() {     cin >> n >> m;     cin >> s;     for (int i = 0; i < m; i++) {       int l, r;       char c1, c2;       cin >> l >> r >> c1 >> c2;       s = change(s, l, r, c1, c2);     }     cout << s;   }   