#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long x1, y1, x2, y2, r;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  unsigned long long d = (y2 - y1) * (y2 - y1) + (x2 - x1) * (x2 - x1);
  double dist = sqrt(d);
  cout << ceil(dist / (2 * r)) << endl;
}
