#include <bits/stdc++.h>
using namespace std;
long double distance(int x, int y, int x1, int y1) {
  long double d;
  d = (x1 - x) * (x1 - x) + (y1 - y) * (y1 - y);
  d = sqrt(d);
  return d;
}
int main() {
  int x, y, x1, y1, r;
  cin >> r >> x >> y >> x1 >> y1;
  long double d, res;
  d = distance(x, y, x1, y1);
  res = ceil(d / (2 * r));
  cout << res;
}
