n = gets.to_i
tmp = gets.split.map(&:to_i)
if tmp.size == n
    puts "\"assert\""
else
    a = $<.map(&:to_i)
    a = tmp + a
    sum = a.inject(:+)
    a = [a[0] + a[1], a[1] + a[2], a[0] + a[2]]
    a.sort!.uniq!
    p a[-2]
end