#include <bits/stdc++.h>
using namespace std;
int main() {
  int T, S, q, tz = 0, cur = 0, n = 1;
  cin >> T >> S >> q;
  cur = S * q;
  while (cur < T) {
    cur = cur * q;
    n++;
  }
  cout << n << endl;
  return 0;
}
