#include <bits/stdc++.h>
int main() {
  int r, x, y, xx, yy;
  scanf("%d %d %d %d %d", &r, &x, &y, &xx, &yy);
  double dx = xx - x;
  double dy = yy - y;
  double dis = std::sqrt(dx * dx + dy * dy);
  printf("%d\n", (int)(dis / (2 * r) + 0.9999999999));
}
