#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  int an =
      ceil(sqrt(((x - x1) * (x - x1)) + ((y - y1) * (y - y1))) / (2.000 * r));
  cout << an;
}
