#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using PII = std::pair<int, int>;
using PLL = std::pair<ll, ll>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)


int main()
{

#ifdef DEBUG
    cout << "DEBUG MODE" << endl;
    ifstream in("input.txt"); //for debug
    cin.rdbuf(in.rdbuf());    //for debug
#endif

    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    a *= b;
    a %= d;
    a *= c;
    a %= d;
    cout << a << endl;

    // for (auto z : rmq)
    //     cout << z << " ";
    // cout << endl;


    return 0;
}