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