#include <bits/stdc++.h>
const double eps = 1e-06;
int main() {
  double t, s, q;
  scanf("%lf%lf%lf", &t, &s, &q);
  double v = (q - 1.0) / q;
  int cnt = 1;
  while (true) {
    s = s / (1 - v);
    if (s > t - eps) break;
    cnt++;
  }
  printf("%d\n", cnt);
  return 0;
}
