import java.util.Scanner;

class no373{
	public static void main(String[] args) {
		Scanner stdIn=new Scanner(System.in);
		long a=stdIn.nextLong(),b=stdIn.nextLong(),c=stdIn.nextLong(),d=stdIn.nextLong();
		System.out.print((a*b)%d*c%d);
	}
}