#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for (int i = a; i < b; i++)
using ll = long long;

int main(){
	int a, b;
	cin >> a  >> b;
	int ans = 0;
	for(int x = 100000; x > 0; x--) {
		if(x % a == b % x) ans = x;
	}
	cout << ans << endl;
}