#include <bits/stdc++.h>
using namespace std;
int main() {
  double x{}, y{}, x1{}, y1{};
  int r{};
  cin >> r >> x >> y >> x1 >> y1;
  double d{};
  d = sqrt(pow((x1 - x), 2) + pow((y1 - y), 2));
  int ans{}, rad{2 * r}, da{int(d)};
  ans = da / (2 * r);
  if (ans * (2 * r) != d) ++ans;
  cout << ans;
  return 0;
}
