## https://yukicoder.me/problems/no/2835


def main():
    N = int(input())
    A = list(map(int, input().split()))

    A.sort()
    answer= 0
    for i in range(N):
        if i % 2 == 0:
            j = i // 2
            answer += A[- j - 1]
        else:
            j = (i - 1) // 2
            answer -= -A[j]
    print(answer)





if __name__ == "__main__":
    main()