#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, s, q, ans = 0;
  cin >> t >> s >> q;
  int downloaded = s;
  while (downloaded < t) {
    downloaded += s * (q - 1);
    s = downloaded;
    ans++;
  }
  cout << ans << endl;
  return 0;
}
