import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long N = sc.nextLong();
		long D = sc.nextLong();
		if(N < D){
			long temp = N;
			N = D;
			D = temp;
		}
		System.out.println(N/gcd(N,D)-1);
	}
	public static long gcd(long N, long D){
		while(D != 0){
			long r = D;
			D = N % D;
			N = r;
		}
		return N;
	}
}