N=int(input())
A=[]

flag=True
for i in range(N):
    try:
        A.append(int(input()))
    except:
        print('"assert"')
        flag=False
        break

import itertools
summary=[]
if flag:
    c=itertools.combinations(A,2)
    for v in c:
        summary.append(v[0]+v[1])
    summary=list(set(summary))
    summary.sort(reverse=True)
    print(summary[1])