#include <iostream>
#include <fstream>

using namespace std;

int gcd(int a, int b, int &x, int &y) {
    if (b==0) {
        x = 1;
        y = 0;
        return a;
    }

    int x0, y0, d;
    d = gcd(b, a%b, x0, y0);

    x = y0;
    y = x0 - (a/b)*y0;

    return d;
}

int main()
{
    ifstream fin("inversmodular.in");
    ofstream fout("inversmodular.out");

    int a, n;
    fin>>a>>n;

    for (int i = 1; i <= n-1; i++) {
        int s = a+i;
        if (n%s==1) {
            fout<<i<<'\n';
            break;
        }
    }
    return 0;
}