#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long int xd = x2 - x1, yd = y2 - y1;
  double dist = sqrt(xd * xd + yd * yd);
  long long int int_part = (int)dist;
  double frac_part = dist - int_part;
  long long int ans;
  ans = int_part / (2 * r);
  if (int_part % (2 * r) == 0 && frac_part == 0) ans--;
  ans++;
  cout << ans << endl;
}
