n = gets.to_i
w = gets.split.map(&:to_i)
total = w.sum

if total % 2 == 1
    puts "impossible"
    exit 0
end

dp = [false] * (total / 2 + 1)
dp[0] = true

w.each do |wi|
    # p wi
    # dp[wi] = true
    (0..(dp.size)).to_a.reverse.each do |num|
        # p "#{wi}, #{num}"
        # p dp
        dp[wi+num] = true if dp[wi]
    end
end
# p dp, w
puts dp[total/2] ? "possible" : "impossible"