#include <bits/stdc++.h>

using ll = long long;

using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll a,b,n{0};
    cin >> a >> b;

    set<ll> s;
    
    int cnt{0};
    while (1)
    {
        n=a*n+b;
        ++cnt;
        if (!n)
            break;
        if (s.find(n)!=s.end())
        {
            cout << "-1\n";
            return 0;
        }
        s.insert(n);
    }

    cout << cnt << "\n";
    
    return 0;
}