import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long a = sc.nextInt();
        long b = sc.nextInt();
        long c = sc.nextInt();
        long d = sc.nextInt();
        a %= d;
        a *= b;
        a %= d;
        a *= c;
        a %= d;
        System.out.println(a);
    }
}