import sys
import math


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    try:
        n = int(input())
        a = [int(input()) for _ in range(n)]
        s = set()
        for i in range(n):
            for j in range(i):
                s.add(a[i] + a[j])
        return sorted(s)[-2]
    except:
        return '"assert"'


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)