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