#include <fstream>

using namespace std;

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

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

    int x1, y1;
    int d = extgcd(b, a % b, x1, y1);

    x = y1;
    y = x1 - y1 * (a / b);

    return d;
}

int modInverse(int a, int n)
{
    int x, y;
    int g = extgcd(a, n, x, y);

    if (g != 1) return -1;

    x %= n;
    if (x < 0) x += n;

    return x;
}

int main(void)
{
    int a, n;

    fin >> a >> n;
    fout << modInverse(a, n);

    return 0;
}