#include <bits/stdc++.h>
using namespace std;
template <typename... T>
void read(T&... args) {
  ((cin >> args), ...);
}
template <typename... T>
void write(T&&... args) {
  ((cout << args << " "), ...);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t, s, q;
  while (cin >> t >> s >> q) {
    int res(1);
    s += s * (q - 1);
    while (t > s) {
      ++res;
      s += s * (q - 1);
    }
    cout << res << endl << endl;
  }
  return 0;
}
