n = gets.to_i
w_list = gets.split.map(&:to_i)
sum = w_list.inject(:+)
dp = Array.new(n, Array.new)
dp[0] = [0]
n.times do |i|
  dp[i+1] = dp[i] + dp[i].map{|a| a + w_list[i]}
end
puts dp[n].include?(sum/2.0) ? 'possible' : 'impossible'