func_code_string: #include <bits/stdc++.h>   using std::cin;   using std::cout;   const int N = 1e5 + 1;   int r, a, b, m, las[N];   int main() {     cin >> a >> b >> m >> r;     memset(las, -1, sizeof las);     las[r] = 0;     for (int i = 1;; ++i) {       r = (a * r + b) % m;       if (~las[r]) {         cout << i - las[r];         return 0;       }       las[r] = i;     }     return 0;   }   