from itertools import combinations


def main():
    N = int(input())
    try:
        A = [int(input()) for _ in range(N)]
    except ValueError:
        print('"assert"')
        return

    A_sum = {first + second for (first, second) in combinations(A, 2)}
    print(sorted(A_sum, reverse=True)[1])


if __name__ == "__main__":
    main()