#include <iostream>

using namespace std;

template <class T>
struct mlcm {
	
	mlcm(T _a, T _b) : a(_a), b(_b) {
		if (a > b) swap(a, b);
		bn = 1;
		blcm = lcm(b+1, a+1);
	}
	
	T gcd(T h, T l) {
		T t;
		while (l) {
			t = l;
			l = h%l;
			h = t;
		}
		return h;
	}
	
	T lcm(T h, T l) {
		return h/gcd(h, l)*l;
	}
	
	T solve() {
		for (T i = 1; i*i < b-a; i++) {
			T x = lcm(b+i, a+i);
			if (x < blcm) {
				blcm = x;
				bn = i;
			}
		}
		return bn;
	}

	T a, b;
	T bn, blcm;	
};

int main()
{
	long long a, b;
	cin >> a >> b;
	mlcm<long long> m(a, b);
	cout << m.solve() << endl;
	return 0;
}