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

def f(n, ws)
  sum = 0; ws.each{ |w| sum += w }
  #puts "  sum=#{sum}->#{sum/2}"
  return false if sum.odd?

  dp = {}
  dp[0] = true

  ws.each do | w |
    dpc = dp.clone
    dpc.keys.each do | d |
      dp[d+w] = dpc[d]
    end
  end
  #dp.sort.each{|k,v| puts "k=#{k}, v=#{v}"}
  return dp[sum/2]
end
puts f(N, W) ? 'possible' : 'impossible'