#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b, c, d;
  cin >> n >> a >> b >> c >> d;
  double p = pow(abs(c - a), 2) + pow(abs(d - b), 2);
  p = sqrt(p);
  int q = ceil(p / (2 * n));
  cout << q;
}
