#include <bits/stdc++.h>
using namespace std;
double jarak;
int r, x, y, xx, yy, tinggi, lebar, ans;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> r >> x >> y >> xx >> yy;
  tinggi = abs(xx - x);
  lebar = abs(yy - y);
  jarak = sqrt(((tinggi * tinggi) + (lebar * lebar)) * 1.0);
  ans = jarak / (2 * r);
  jarak -= ans * (2 * r);
  if (jarak > 0) {
    ans++;
  }
  cout << ans << '\n';
  return 0;
}
