#include <bits/stdc++.h>
using namespace std;
int main() {
  long long a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;
  a *= 2;
  long double dist = ((d - b) * (d - b)) + ((e - c) * (e - c));
  dist = sqrt(dist);
  long long q = (int)dist;
  dist -= (int)dist;
  if (dist) q++;
  if (q % a)
    cout << (q / a) + 1 << endl;
  else
    cout << q / a << endl;
}
