using System;
using System.Collections.Generic;
using System.Linq;

class Program {
    static string ReadLine() { return Console.ReadLine(); }
    static int ReadInt() { return int.Parse(ReadLine()); }
    static int[] ReadInts() { return ReadLine().Split().Select(int.Parse).ToArray(); }
    static string[] ReadStrings() { return ReadLine().Split(); }

    static void Main() {
        var xs = ReadLine().Split().Select(long.Parse).ToArray();
        long a = xs[0];
        long b = xs[1];
        long c = xs[2];
        long d = xs[3];

        long x = (a * b) % d;
        long y = (x * c) % d;
        Console.WriteLine(y);        
    }
}