#include <iostream>
#include <fstream>

using namespace std;

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

int gcdExtended(int a, int n, int &x, int &y)
{
    if(a == 0)
    {
        x = 0;
        y = 1;
        return n;
    }
    int x1, y1;
    int gcd = gcdExtended(n % a, a, x1, y1);
    x = y1 - x1 * (n / a);
    y = x1;
    return gcd;
}

int modInv(int a, int n)
{
    int x, y;
    int gcd = gcdExtended(a, n, x, y);

    if(gcd != 1)
        return -1;
    else
        return (1ll * x + n) % n;
}

int main()
{
    int  a, n;
    fin >> a >> n;

    fout << modInv(a, n) << '\n';
    return 0;
}