# frozen_string_literal: true

def solve
  if W.sum.even? && W.balancable?
    'possible'
  else
    'impossible'
  end
end

class Array
  def balancable?
    (1..size / 2).any? do |left|
      combination(left).any? { 2 * _1.sum == sum }
    end
  end
end

N = gets.to_i
W = gets.split.map(&:to_i)

puts solve