#include <bits/stdc++.h>
int main() {
  double a, b, c, d, e;
  scanf("%lf %lf %lf %lf %lf", &a, &b, &c, &d, &e);
  printf(
      "%d",
      (ceil((double(sqrt((b - d) * (b - d) + (c - e) * (c - e))) / (2 * a)))));
  return 0;
}
