n=int(input())
a=list(map(int,input().split()))
if len(a)==n:
    print('"assert"')
else:
    b=[a[0]]+[int(input()) for _ in range(n-1)]
    c=[]
    for i in range(n):
        for j in range(i+1,n):
            c.append(b[i]+b[j])
    c=list(set(c))
    c.sort(reverse=True)
    print(c[1])