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