#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double x, y, xx, yy, r;
  cin >> r >> x >> y >> xx >> yy;
  double d = (x - xx) * (x - xx) + (y - yy) * (y - yy);
  d = sqrt(d);
  d /= (2 * r);
  if (d > (int)d) {
    d = (int)d + 1;
  }
  d = (int)d;
  cout << d << "\n";
  return 0;
}
