n = int(input())
A = list(map(int, input().split()))
if len(A) != 1:
    print('"assert"')
else:
    for i in range(n - 1):
        A.append(int(input()))
    S = set()

    for i in range(n):
        for j in range(i + 1, n):
            S.add(A[i] + A[j])
    print(sorted(S)[-2])