


import java.util.Scanner;

public class b{
   public static void main (String args[])
 {
     Scanner in = new Scanner (System.in);
     long r=in.nextLong(),x=in.nextLong(),y=in.nextLong(), x1=in.nextLong(), y1=in.nextLong();
     System.out.println((long)Math.ceil(Math.sqrt(Math.pow(x-x1, 2)+Math.pow(y-y1, 2))/(2*r)));   
 }
}




