import java.util.*;

public class example3 {


    static void printFirst(LinkedList<? extends Number> n) {
        Number e = n.getFirst();
        System.out.println(e);
    }


    public static void main(String[] a) {
        LinkedList<Double> ld = new LinkedList<Double>();
        ld.add( 2.71 );
        printFirst( ld );
         
        LinkedList<Integer> li = new LinkedList<Integer>();
        li.add( 21 );
        printFirst( li );
    }

}