#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, p, q;
  cin >> r >> x >> y >> p >> q;
  double dist = hypot(abs(p - x), abs(q - y));
  int ans = ceil(dist / (2 * r));
  cout << ans << endl;
  return 0;
}
