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