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