#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  long long r, first, second, a, b;
  cin >> r >> first >> second >> a >> b;
  cout << ceil((sqrt((first - a) * (first - a) + (second - b) * (second - b)) /
                (r * 2.0)))
       << "\n";
}
