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