#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
int main() {
  long long A,B,C,D; cin >> A >> B >> C>> D;
  long long x = (A * B) % D;
  long long y = (x * C) % D;
  cout << y << endl;
}