#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, x1, y, y1, ans;
  double distance;
  cin >> r >> x >> y >> x1 >> y1;
  distance = sqrt(pow(y - y1, 2.0) + pow(x - x1, 2.0));
  ans = ceil(distance);
  cout << ans / (2 * r) << endl;
  return 0;
}
