#include<bits/stdc++.h> using namespace std; int main() { long long n, k; cin >> n >> k; if (n == 1) { cout << 0 << endl; return 0; } if (k == 0) { cout << -1 << endl; return 0; } long long time = 0; long long total = 1; while (total < n) { long long add = total * k; total += add; time++; if (total > 1e18) { break; } } cout << time << endl; return 0; }