import java.util.*;
import java.io.*;
public class Main 
{ 
public static void main(String args[]) throws java.lang.Exception
     {
        Scanner sc=new Scanner(System.in);
        PrintWriter out=new PrintWriter(System.out);
        double r=sc.nextInt();
        double x=sc.nextInt();
        double y=sc.nextInt();
        double xx=sc.nextInt();
        double yy=sc.nextInt();
        double dis=Math.sqrt((xx-x)*(xx-x)+(yy-y)*(yy-y));
        out.println((int)Math.ceil(dis/(2*r)));
        out.flush();
     }
}