import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	int d = sc.nextInt();
    	System.out.println(getLCM(n, d) / d - 1);
	}
	
	static long getLCM(long x, long y) {
	    return x / getGCD(x, y) * y;
	}
	
	static long getGCD(long x, long y) {
	    if (x % y == 0) {
	        return y;
	    } else {
	        return getGCD(y, x % y);
	    }
	}
}