#include <fstream>

using namespace std;

#define INFILE "inversmodular.in"
#define OUTFILE "inversmodular.out"
#define ll long long

ifstream fin (INFILE);
ofstream fout (OUTFILE);

ll a, n;

void solve(){

    fin >> a >> n;

    for(ll x = 1; x <= n - 1; ++x){
        if((a * x) % n == 1){
            fout << x << '\n';
            return;
        }
    }

    fout << -1 << '\n';

}

int main(){
    solve();
    return 0;
}