#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  cout << ceil(d / (double)(2 * r));
}
