#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x, y, x1, y1;
  cin >> r;
  cin >> x;
  cin >> y;
  cin >> x1;
  cin >> y1;
  double m = sqrtl((x - x1) * (x - x1) + (y - y1) * (y - y1));
  m = m / (2 * r);
  cout << ceil(m) << "\n";
}
