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