n = int(input())

s = [0] * n
for i in range(n):
    a = input()
    if len(a) > 1:
        print("assert")
        exit()
    else:
        s[i] = int(a)

s.sort(reverse=True)
t = set()
for i in range(n):
    for j in range(i+1, n):
        t.add(s[i] + s[j])

ans = list(t)
ans.sort(reverse=True)
print(ans[1])