func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     long long a, b, m, r0;     cin >> a >> b >> m >> r0;     int step = 0;     map<int, int> smap;     smap[r0] = 0;     while (true) {       r0 = r0 * a + b;       r0 %= m;       step++;       if (smap.find(r0) != smap.end()) {         cout << step - smap[r0];         break;       }       smap[r0] = step;     }     return 0;   }   