class Calc0004
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @n = args.shift.first.to_i
    @ws = args.shift.map(&:to_i)
    @memo = Hash.new
  end

  def calc
    total = @ws.inject(:+)
    return false unless total.even?
    @half = total / 2
    dp(0, 0)
  end

  def dp(k, sum)
    if k >= @n || sum > @half
      res = false
    elsif sum == @half
      res = true
    elsif !@memo[[k, sum]].nil?
      res = @memo[[k, sum]]
    else
      res = dp(k + 1, sum) || dp(k + 1, sum + @ws[k])
    end
    @memo[[k, sum]] = res
  end

  def run
    calc ? 'possible' : 'impossible'
  end
end

puts Calc0004.new(STDIN.readlines).run if __FILE__ == $0