import java.io.*;
import java.util.*;

public class AmrPins {
    public static void main(String args[])throws Exception
    {
     BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
     String line1=br.readLine();
     String lines[]=line1.split(" ");
     int r=Integer.parseInt(lines[0]);
     int x=Integer.parseInt(lines[1]);
     int y=Integer.parseInt(lines[2]);
     int xd=Integer.parseInt(lines[3]);
     int yd=Integer.parseInt(lines[4]);
     double d=Math.sqrt( Math.pow(xd-x, 2) + Math.pow(yd-y, 2) );
     int dis=(int)Math.ceil(d);
     if(x==xd && y==yd)
         System.out.println(0);
     else
     {

       int out=0;
       while(dis>0)
       {
         dis-=2*r;
         out++;
       }
       System.out.println(out);
     }
    }
    
}
