#include <bits/stdc++.h>
using namespace std;
int main() {
  int T, S, q, x, ans;
  while (scanf("%d%d%d", &T, &S, &q) != EOF) {
    ans = 1;
    x = q * S;
    while (x < T) {
      x = q * x;
      ans++;
    }
    printf("%d\n", ans);
  }
  return 0;
}
