using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        for (var i = 0; i < c[0] * c[1]; ++i)
        {
            if (i % c[0] == c[2] && i % c[1] == c[3])
            {
                WriteLine(i);
                return;
            }
        }
    }
}