Problem:
Score: 200 points

Problem Statement

We have N cards. A number a_i is written on the i-th card.

Alice and Bob will play a game using these cards. In this game, Alice and Bob alternately take one card. Alice goes first.

The game ends when all the cards are taken by the two players, and the score of each player is the sum of the numbers written on the cards he/she has taken. When both players take the optimal strategy to maximize their scores, find Alice's score minus Bob's score.

Constraints

N is an integer between 1 and 100 (inclusive).

a_i \ (1 \leq i \leq N) is an integer between 1 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 a_3 ... a_N

Output

Print Alice's score minus Bob's score when both players take the optimal strategy to maximize their scores.

Sample Input 1

2
3 1

Sample Output 1

2

First, Alice will take the card with 3. Then, Bob will take the card with 1.
The difference of their scores will be 3 - 1 = 2.

Sample Input 2

3
2 7 4

Sample Output 2

5

First, Alice will take the card with 7. Then, Bob will take the card with 4. Lastly, Alice will take the card with 2. The difference of their scores will be 7 - 4 + 2 = 5. The difference of their scores will be 3 - 1 = 2.

Sample Input 3

4
20 18 2 18

Sample Output 3

18

Solution in Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program main
  implicit none
  
  integer :: n,i,j,t,a(100) = 0,al=0,bo=0,endal,endbo
  
  read(*,*)n
  read(*,*)(a(i),i=1, n)
  
  if (n == 1) then
    write(*,*)a(i)
    stop
  end if
  
  do i=1,N-1
     do j=i+1,N
        if(a(i) .gt. a(j))then
           t=a(i)
           a(i)=a(j)
           a(j)=t
        end if
     end do
  end do
  if (mod(n,2)==0) then
    endal = 2
    endbo = 1
  else
    endal = 1
    endbo = 2
  end if
  do i = n, endal, -2
    al = al + a(i)
  end do
  
  do i = n-1, endbo, -2
    bo = bo + a(i)
  end do
  write(*,*)al-bo
end program main