#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

ll a, b, c, d, ans;

int main() {
  cin >> a >> b >> c >> d;
  ans = a * b % d;
  ans = ans * c % d;
  ans %= d;
  cout << ans << endl;
  return 0;
}