#include <bits/stdc++.h>
int main() {
  int r, x, y, xd, yd;
  scanf("%d %d %d %d %d", &r, &x, &y, &xd, &yd);
  std::cout << ceil(sqrt(pow(fabs(xd - x), 2) + pow(fabs(yd - y), 2)) /
                    (2 * r));
}
