#include <bits/stdc++.h>
using namespace std;
int main() {
  double m, n;
  long long int r, a, b, c, d, dist, sim;
  cin >> r >> a >> b >> c >> d;
  dist = (c - a) * (c - a) + (d - b) * (d - b);
  m = sqrt(dist);
  m = m / 2;
  c = m / r;
  m = m / r;
  if (m == c)
    cout << c;
  else
    cout << c + 1;
  return 0;
}
