require 'prime'

ps = Prime.each(10**7).each_cons(2).filter { _2 - _1 == 2 }.map { _1 * _2 }

t = gets.to_i
qs = t.times.map { gets.to_i }
a = []
qs.each do |q|
  id = ps.bsearch_index { _1 > q }
  id ||= ps.size
  a << (id > 0 ? ps[id - 1] : -1)
end
puts a