#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
int want, delay, rate;
void run() {
  scanf("%d%d%d", &want, &delay, &rate);
  int ret = 1, have = delay;
  while (have * rate < want) ++ret, have *= rate;
  printf("%d\n", ret);
}
int main() {
  run();
  return 0;
}
