#include <bits/stdc++.h>
using namespace std;
int a[100000];
int main() {
  long long int t, q, s, count = 1, current;
  cin >> t >> s >> q;
  current = q * s;
  while (current < t) {
    current = current * q;
    count++;
  }
  cout << count << endl;
}
