#include <bits/stdc++.h>
using namespace std;
int main() {
  long t, s, q, ans = 1, x;
  scanf("%ld %ld %ld", &t, &s, &q);
  while (1) {
    x = s * q;
    if (x >= t) {
      printf("%ld", ans);
      break;
    } else {
      ans++;
      s = x;
    }
  }
}
