import itertools


def solve(xs):
    ss = sorted(set(x + y for x, y in itertools.combinations(xs, 2)), reverse=True)
    return ss[1]


def main():
    n = int(input())
    res = None
    try:
        xs = [int(input()) for _ in range(n)]
        res = solve(xs)
    except ValueError:
        print('"assert"')
    else:
        print(res)


if __name__ == "__main__":
    main()