import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int r = in.nextInt();
    int x0 = in.nextInt();
    int y0 = in.nextInt();
    int x1 = in.nextInt();
    int y1 = in.nextInt();
    double distance = Math.sqrt((x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1));
    System.out.println((long) Math.ceil(distance / r / 2));
  }
}
