#include <stdio.h>

long gcd(long x,long y)
{
	long r;
	if(y>x){
		r=x;
		x=y;
		y=r;
	}
	while(y>0){
		r=x%y;
		x=y;
		y=r;
	}
	return x;
}

long lcm(long x,long y)
{
	return x*y/gcd(x,y);
}

int main(void)
{
	long n,d;
	scanf("%ld%ld",&n,&d);
	printf("%ld",lcm(n,d)/d-1);
	return 0;
}