#include <bits/stdc++.h>

using namespace std;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  }
} initializer;

int main() {
  int64_t a, b, c, d;
  cin >> a >> b >> c >> d;
  cout << a * b % d * c % d << endl;
}