#include <iostream>
#define EN unsigned long int
using namespace std;

EN LCM(EN, EN);
EN GCD(EN, EN);

int main() {
	EN a, b, def_lcm=0, aux;
	double counter = 1.0, n = 0.0;
	bool found_answer=false;
	cin >> a >> b;
	def_lcm = LCM(a, b);
	if (a > b) {
		aux = a;
		a = b;
		b = aux;
	}
	while (counter < def_lcm) {
		++counter;
		n = (b - (counter*a)) / (counter - 1);
		//cout << n << endl;
		if ((n > 0) && (n == (int)n)) {
			found_answer = true;
			break;
		}
	}
	if (!found_answer) n = 0;
	cout << n << endl;
	return 0;
}


EN GCD(EN a, EN b) {
	EN c = 0;
	while (a%b != 0) {
		c = b;
		b = a%b;
		a = c;
	}
	return b;
}

EN LCM(EN a, EN b) {
	return (a*b) / GCD(a, b);
}