#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2, m;
  double d, n;
  cin >> r;
  cin >> x1;
  cin >> y1;
  cin >> x2;
  cin >> y2;
  d = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
  n = (d / (2 * r));
  m = ceil(n);
  cout << m << endl;
  return 0;
}
