import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long a = in.nextLong();
        long b = in.nextLong();
        long c = in.nextLong();
        long d = in.nextLong();

        System.out.println((a*b)%d*(c%d));

        in.close();
    }
}