import java.util.Scanner;
public class Main {
		public static void main(String[] args) {
			Scanner sc = new Scanner(System.in);
			long N = sc.nextInt();
			long D = sc.nextInt();
			long ans = 0;
			long gcd = gcd(N,D);
			N *= D / gcd;
			
			System.out.println(N / D - 1);
			
		}
		static long gcd(long a, long b) {
			if(a < b) return gcd(b,a);
			if(b == 0) return a;
			return gcd(b, a % b);
		}
}