Please help (using recursion)

You are given an Array of 2N positive integers.There are N rounds in total.You have to choose any 2 positive integers from an array and delete them.
Your score in each round will be gcd(num1,num2) * round_number where num1 and num2 are the. number you have chosen and round_number is the current round. Your total score will be the summation that you have obtained in every round.
Determine the total score.
Round starts from 1.
EXAMPLE

N=3
A=[8 5 6 25 6 16]

ROUND 1 = gcd(5,25) Round_number = 5 1=5
ROUND 1 = gcd(6,6) Round_number = 6 2=12
ROUND 1 = gcd(8,16) Round_number = 8 3=24

MAXIMUM= 5+12+24= 41

EXAMPLE 2

N=
A=[3 4 9 5]

ROUND 1 = gcd(4 ,5 ) Round_number = 1 1=1
ROUND 1 = gcd(3,9) Round_number = 3 2=6

MAXIMUM=1+6=7