#include <bits/stdc++.h>
using namespace std;

int main() {
    int n = 0, a, b, ans = 0;
    cin >> a >> b;
    for (;;) {
        n = a * n + b;
        ans++;
        if (n == 0 || ans >= 1000) break;
    }
    if (ans == 1000) {
        cout << -1 << endl;
    } else {
        cout << ans << endl;
    }
}