#include <bits/stdc++.h>
const double EPS = 1e-9;
double T, S, Q;
int main() {
  while (scanf("%lf%lf%lf", &T, &S, &Q) == 3) {
    int ans = 1;
    double now = 0.0;
    for (;;) {
      const double t = S - now;
      now += t * Q, S += t * (Q - 1.0);
      if (S + EPS > T) break;
      ans++, now = 0.0;
    }
    printf("%d\n", ans);
  }
  return 0;
}
