import java.util.Scanner;

public class Yuki373{
 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();
  System.out.println(a*b%d*c%d);
 }
}