#include <bits/stdc++.h>
using namespace std;
int t, s, p;
int main() {
  scanf("%d %d %d", &t, &s, &p);
  int l = t;
  int x1 = 0, x2 = s;
  int co = 1;
  while (x1 < l) {
    x1 = x1 + p;
    x2 = x2 + p - 1;
    if (x1 >= l && x2 >= l)
      break;
    else if (x1 >= x2) {
      x1 = 0;
      co++;
    }
  }
  cout << co << endl;
  return 0;
}
