#include <iostream>

using namespace std;

int main()
{
    int a, b, n, n1;
    cin >> a >> b;

    n1 = (a+1)*(b+1);

    if(a > b)
    {
        a ^= b;
        b ^= a;
        a ^= b;
    }
    n = 1;
    while((b+n)%(a+n) && (b+n <= n1))
        ++n;
    if(b+n > n1)
        cout << 1;
    else
        cout << n;
    return 0;
}