using System;
public class Program
{
    static void Main()
    {
        string s = Console.ReadLine();
        string[] t = s.Split(' ');
        int a = int.Parse(t[0]);
        int b = int.Parse(t[1]);
        
		var Max = a+b;
		for (var x = 1; x < Max; x++)
		{
			var moda = x % a;
			if (moda == x % b)
			{
        		Console.WriteLine(moda);
				break;
			}
		}
    }
}