#include <bits/stdc++.h>
using namespace std;
using LL=long long;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
int main()
{
	LL A, B, C, D;
	cin >> A >> B >> C >> D;
	cout << ( ( A * B % D ) * C ) % D << endl;
	return 0;
}