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