n = gets.not_nil!.to_i
w = gets.not_nil!.split.map(&.to_i)

# if w.size != n
#   puts "Error: Expected #{n} numbers but got #{w.size}"
#   exit
# end

t = w.sum
if t.odd?
  puts "impossible"
  exit
end

th = t // 2

# Create a 2D array with n+1 rows and th+1 columns, initialized to 0
m = Array(Array(Int32)).new(n + 1) { Array(Int32).new(th + 1, 0) }

(1...n).each do |i|
  (0..th).each do |j|
    if j < w[i]
      m[i][j] = m[i - 1][j]
    else
      m[i][j] = Math.max(m[i - 1][j - w[i]] + w[i], m[i - 1][j])
    end

    if m[i][j] == th
      puts "possible"
      exit
    end
  end
end

puts "impossible"