#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double distance = sqrt(((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)) /
                         (double)(4 * r * r));
  int ans = ceil(distance);
  cout << ans << endl;
}
