# include <iostream>
# include <cstring>
# include <string>
# include <vector>
# include <cmath>
# include <sstream>
# include <iomanip>
# include <algorithm>
using namespace std;

# define repl(i, a, b)	for(int i=(int)(a);i<(int)(b);i++)
# define rep(i, n)	repl(i, 0, n)
typedef long long ll;

int main(){
	ll a, b, c, d;
	cin >> a >> b >> c >> d;
	a *= b;
	a %= d;
	cout << a*c%d << endl;
	return 0;
}