import java.util.*;
public class Solution
{
         public static void main(String args[])
         {
                  Scanner scan=new Scanner(System.in);
                  long r=scan.nextLong();
                  long x=scan.nextLong();
                  long y=scan.nextLong();
                  long x1=scan.nextLong();
                  long y1=scan.nextLong();
                  double d=Math.sqrt(((x1-x)*(x1-x))+((y1-y)*(y1-y)));
                  System.out.println((long)Math.ceil(d/(2*r)));
                  
         }
}