import java.util.ArrayList;
import java.math.BigInteger;
public class LP1Practice
{
    /** 
     * Da main
     */
    public static void main(String[] args)
    {   
        //use this for any test code.  
    }   
    /** 
     * This function pulls out all characters of even index
     * and returns them bundled in a string
     * @param s the string you are sampling from
     * @return a string containing all characters, in order,
     * from s.
     */
    public static String everyOther(String s)
    {   
        return "";
    }   
    /** 
     * This functon tests if the BigInteger passed it is a power of 2.
     * @param b is a BigInteger
     * @return true if b is a power of 2 and false otherwise.
     */
    public static boolean isAPowerOf2(BigInteger b)
    {   
        return false;
    }
    /*
     * This function returns a new array list with
     * all elements from the array list a that are greater
     * than or equal to n.
     * @param a an array list of integers
     * @param n an integer
     * @return a new array list with all entries in a that are n or larger.
     */
    public static ArrayList<Integer> largerThan(ArrayList<Integer> a, int n)
    {
        return null; 
    }
    /**
     * This returns the nth Fibonacci number as a BigInteger
     * @param a positive integer
     * @return the nth Fibnacci number. 
     * fib(0) -> 0
     * fib(1) -> 1
     * fib(2) -> 1 etc
     */
    public static BigInteger fibonacci(int n)
    {
        return null;
    }
    /**
    * This returns the sum of alll of the gcd's of the elements in the list al
    * with the given BigInteger b.
    * @param al a list of BigIntegers
    * @b a BigInteger 
    * @return the sum of the GCDs of the elemnts in al with b.
    * Sample  a = [34, 21, 65]
    * b = 13
    * returns 5.
    */
    public static BigInteger sumGCD(BigInteger b, ArrayList<BigInteger> al)
    {   
        return null;
    }
}