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