#include <bits/stdc++.h>
const int maxn = 1e5 + 100, mod = 1e9 + 7;
using namespace std;
int main() {
  int T, S, q;
  cin >> T >> S >> q;
  int res = 1;
  long long download = (long long)S * q;
  while (T > download) {
    res++;
    download *= q;
  }
  cout << res << endl;
  return 0;
}
