#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cout.precision(20);
  int r, x, y, x1, y1;
  int d, h;
  cin >> r >> x >> y >> x1 >> y1;
  r = r * 2;
  h = d = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  d = sqrt(d);
  if (h != d * d) d++;
  h = d / r;
  if (d % r != 0) h++;
  cout << h;
}
