N=int(input())
li=[]
for i in range(N):
    S=input()
    if " " in S:
        print('"assert"');exit()
    else:
        li.append(int(S))
ans=set()
for i in range(N-1):
    for k in range(i+1,N):
        ans.add(li[i]+li[k])
ans=list(ans)
ans.sort(reverse=True)
print(ans[1])