import java.util.Scanner;

public class Main {

  public static void main(String args[])
  {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int x = sc.nextInt();int y = sc.nextInt();int x1 = sc.nextInt(); int y1 = sc.nextInt();
    double d = Math.sqrt(Math.pow((x1-x),2)+Math.pow((y1-y),2));
    System.out.println((int)Math.ceil(d/(2*n)));
  }
  }
