using System;

class Pyon
{
	static void Main(String[] args)
	{
		long N, D;
		String [] vals = Console.ReadLine().Split(' ');

		N = long.Parse(vals[0]);
		D = long.Parse(vals[1]);

		Console.WriteLine(N/gcd(N,D)-1);
	}


	static long gcd(long a, long b)
	{
		if(b == 0)
			return a;

		return gcd(b, a%b);
	}
}