#include <bits/stdc++.h>
using namespace std;
int main(int argc, char const *argv[]) {
  int t, q, s;
  cin >> t >> s >> q;
  int steps = 1;
  while (true) {
    if (s + s * (q - 1) < t)
      steps++;
    else
      break;
    s = s + s * (q - 1);
  }
  cout << steps << endl;
  return 0;
}
