#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  int dis = sqrt(pow((xx - x), 2) + pow((yy - y), 2));
  cout << dis / (2 * r) + ((dis % (2 * r) == 0) ? 0 : 2);
}
