#include <bits/stdc++.h>
using namespace std;
const long double eps = 0.00000001;
int main() {
  long double dd;
  int a, b, c, d, e;
  cin >> a >> b >> c >> d >> e;
  long double d1 = b - d, d2 = c - e;
  dd = sqrt(d1 * d1 + d2 * d2);
  int dis = dd + eps;
  int res = dis / (2 * a);
  if (dd - dis > 2 * eps || dis % (2 * a)) res++;
  cout << res << endl;
}
