#include <bits/stdc++.h>
using namespace std;
int main() {
  double x1, y1, x2, y2, r, ans;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  ans = ceil(sqrt(((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))));
  cout << ceil(ans / (2 * r)) << endl;
  return 0;
}
