#include <iostream>
using namespace std;
typedef unsigned long long UL;
int main(int argc, char* argv[])
{
	UL A,B,C,D;
	cin>>A>>B>>C>>D;
	UL X=A;
	X*=B;
	X%=D;
	X*=C;
	X%=D;
	cout<<X<<endl;
	return 0;
}