#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d = sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2));
  double ans;
  ans = ceil(d / (2.0 * (double)r));
  cout << ans;
  return 0;
}
