
import java.util.*;
/**
 * Created by Hp on 5/5/2016.
 */
public class AMrAndPins {
    public static void main(String [] sr){
        Scanner s=new Scanner(System.in);
        int r=s.nextInt();
        int x=s.nextInt();
        int y=s.nextInt();
        int xx=s.nextInt();
        int yy=s.nextInt();
        double d=Math.sqrt(Math.pow(xx-x,2)+Math.pow(yy-y,2));
        System.out.println((int)Math.ceil(d/(2*r)));
    }
}
