#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long double d, r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  cout << ceil(d / (2.0 * r)) << endl;
}
