#include <bits/stdc++.h>
using namespace std;
double r, x, _x, y, _y, d;
int ans;
int main() {
  if (0) {
    freopen(
        "/Users/manuelalejandrovergaradiaz/Documents/Manu/Programation/"
        "Programation/Programation/autocomplete.txt",
        "r", stdin);
    freopen(
        "/Users/manuelalejandrovergaradiaz/Documents/Manu/Programation/"
        "Programation/Programation/output",
        "w", stdout);
  }
  cin >> r >> x >> y >> _x >> _y;
  d = sqrt((_x - x) * (_x - x) + (_y - y) * (_y - y));
  ans = d / (2 * r) + (d > (double)(2 * r));
  cout << ans << endl;
  return 0;
}
