from itertools import combinations


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

    sums = {sum(x) for x in combinations(arr, 2)}
    print(sorted(sums, reverse=True)[1])


if __name__ == "__main__":
    main()