#include <bits/stdc++.h>
using namespace std;
int main() {
  long double a, b, r, x, y, h1;
  long h2;
  cin >> r >> x >> y >> a >> b;
  h1 = (hypotl((a - x), (b - y))) / (2 * r);
  h2 = (long)h1;
  if ((long double)h2 == h1) {
    cout << h2;
  } else
    cout << (h2 + 1);
  return 0;
}
