#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float distance = sqrt((float)((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)));
  int ans = ceil(distance / (2 * r));
  cout << ans << endl;
}
