import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {
	
	public static long gcd(long a, long b){
		return b == 0 ? a : gcd(b, a % b);
	}
	public static long lcm(long a, long b){
		return a / gcd(a, b) * b;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final long N = sc.nextLong();
		final long D = sc.nextLong();
		
		System.out.println((lcm(N, D) / D) - 1);
		
	}
}