#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios::sync_with_stdio(false);
  int T, S, q;
  cin >> T >> S >> q;
  int num = 1;
  long long i = q * S;
  while (i < T) {
    num++;
    i *= q;
  }
  cout << num << endl;
}
