#include <bits/stdc++.h>
using namespace std;
int main() {
  int t, s, q, f;
  f = 0;
  int ans = 1;
  scanf("%d%d%d", &t, &s, &q);
  while (1) {
    s += q - 1;
    f += q;
    if (s >= t) {
      break;
    }
    if (s <= f) {
      ans++;
      f = 0;
    }
  }
  printf("%d\n", ans);
  return 0;
}
