#include <bits/stdc++.h>
const double EPS = 1e-5;
const long long mod = 1000000007ll;
const double PI = 3.14159265359;
int INF = 2147483645;
template <class T>
T Max2(T a, T b) {
  return a < b ? b : a;
}
template <class T>
T Min2(T a, T b) {
  return a < b ? a : b;
}
template <class T>
T Max3(T a, T b, T c) {
  return Max2(Max2(a, b), c);
}
template <class T>
T Min3(T a, T b, T c) {
  return Min2(Min2(a, b), c);
}
template <class T>
T Max4(T a, T b, T c, T d) {
  return Max2(Max2(a, b), Max2(c, d));
}
template <class T>
T Min4(T a, T b, T c, T d) {
  return Min2(Min2(a, b), Max2(c, d));
}
using namespace std;
int gcd(int a, int b) {
  if (b == 0) return a;
  a %= b;
  return gcd(b, a);
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  int t, s, q;
  cin >> t >> s >> q;
  int start = 0;
  while (s < t) {
    s = s * q;
    start++;
  }
  if (start == 0) {
    cout << start + 1 << endl;
    return 0;
  }
  cout << start << endl;
  return 0;
}
