n = gets.chomp.to_i
ws = gets.chomp.split.map(&:to_i)

possible = Array.new(2){Array.new(10001, false)}
possible[0][0] = true

s = 0
(0...n).to_a.each do |i|
  w = ws[i]
  for j in 0..s
    possible[(i + 1) % 2][j] = false
  end
  for j in 0..s
    if possible[i % 2][j]
      possible[(i + 1) % 2][j + w] = true
      possible[(i + 1) % 2][(j - w).abs] = true
    end
  end
  s += w
end

puts possible[n % 2][0] ? 'possible' : 'impossible'