#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double mx = (x1 - x2) * (x1 - x2);
  double my = (y1 - y2) * (y1 - y2);
  double d = mx + my;
  double p = sqrt(d);
  double dd = 2 * r;
  long long int ans = ceil(p / dd);
  cout << ans << endl;
  return 0;
}
