import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		final long A = sc.nextLong();
		final long B = sc.nextLong();
		final long C = sc.nextLong();
		final long D = sc.nextLong();
		
		System.out.println((((A * B) % D) * C) % D) ;
	}

}