#include <bits/stdc++.h>
int main() {
  double r, x2, y2, x1, y1, d;
  double s, b;
  int a;
  scanf("%lf%lf%lf%lf%lf", &r, &x1, &y1, &x2, &y2);
  d = sqrt((y2 - y1) * (y2 - y1) + (x2 - x1) * (x2 - x1));
  s = d / r / 2;
  a = (int)s;
  b = (double)a;
  if (b < s) b += 1;
  printf("%.0lf\n", b);
  return 0;
}
