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