#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  int r, x, y, p, q;
  float ans;
  cin >> r >> x >> y >> p >> q;
  int a = p - x;
  int b = q - y;
  float f = pow(a, 2) + pow(b, 2);
  float rt = (sqrt(f));
  ans = (rt / (2 * r));
  cout << ceil(ans);
  return 0;
}
