
/*
 *   
 *   Date: 07 September 2019
 *   Time: 01:03:00
*/
import java.io.*; 
import java.util.*;


   
public class AmarAndPins 
{
    public static void main(String[] args) throws NumberFormatException, IOException
    { 
        Scanner sc=new Scanner(System.in);
       int r=sc.nextInt();
       int x=sc.nextInt();
       int y=sc.nextInt();
       int x1=sc.nextInt();
       int y1=sc.nextInt();
        System.out.println((int)(Math.ceil(Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y))/(2*r))));

    } 
} 
 
 
 
