#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  double d = sqrt(((x - a) * (x - a)) + ((y - b) * (y - b)));
  int ans = ceil(d / (2 * r));
  cout << ans;
}
