import java.util.*;
public class sol
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        int r,x1,y1,x2,y2;
        r=sc.nextInt();
        x1=sc.nextInt();
        y1=sc.nextInt();
        x2=sc.nextInt();
        y2=sc.nextInt();
        
        double dist=(Math.sqrt(((x2-x1)*(x2-x1))+((y2-y1)*(y2-y1)))/r)/2;
        int ans=(int)Math.ceil(dist);
        System.out.println(ans);
        
    }
}