#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  if (x1 == x2)
    cout << ceil(abs(y1 - y2) / (2 * r));
  else if (y1 == y2)
    cout << ceil(abs(x1 - x2) / (2 * r));
  else
    cout << ceil(pow((y1 - y2) * (y1 - y2) + (x1 - x2) * (x1 - x2), 0.5) /
                 (2 * r));
  return 0;
}
