#include<iostream>
#include<cmath>
#include<vector>
#include<string>
#include<set>
#include<iomanip>
#include<algorithm>
using namespace std;
int main() {
    long long a, b, c, d; cin >> a >> b >> c >> d;
    cout << a*b%d*c%d<< endl;
    return 0;
}