#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const double pi = 3.14159265358979323846;
const int maxn = 2e5 + 5;
double t, s, q;
int main() {
  int a, b;
  while (~scanf("%lf%lf%lf", &t, &s, &q)) {
    int ans = 0;
    double tp = s * q;
    ans++;
    while (tp - t < -(1e-10)) {
      ans++;
      tp = q * tp;
    }
    printf("%d\n", ans);
  }
}
