// yukicoder
#include <bits/stdc++.h>
#define ll long long
using namespace std;

int main() {
    ll a, b, c, d;
    cin >> a >> b >> c >> d;

    ll res = a % d;
    res *= b;
    res %= d;
    res *= c;
    res %= d;

    cout << res << "\n";

    return 0;
}