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