## https://yukicoder.me/problems/no/2840


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

    sum_a = sum(A)

    A.sort()

    dp = {0}
    ans = float("inf")
    for a in A:
        new_dp = {key + a for key in dp}

        for k in new_dp:
            if k in dp:
                ans = min(ans, k)
            else:
                dp.add(k)
        if ans < float("inf"):
            break

    if ans == float("inf"):
        print(-1)
    else:
        answer = sum_a - 2 * ans
        if answer == 0:
            print(-1)
        else:
            print(answer)
        







if __name__ == '__main__':
    main()