inputs = STDIN.readlines.map(&:chomp)
N = inputs[0].to_i
Ws = inputs[1].split(/\s+/).map(&:to_i)

total = Ws.inject(:+)
unless total % 2 == 0
  puts 'impossible'
  exit
end

goal = total / 2
memos = Array.new(N + 1) { Hash.new }

def dp(i, g, memos)
  if g == 0
    res = true
  elsif i == N || g < 0
    res = false
  elsif memos[i].key?(g)
    res = memos[i][g]
  else
    res = dp(i + 1, g, memos) || dp(i + 1, g - Ws[i], memos)
  end
  memos[i][g] = res
end

puts dp(0, goal, memos) ? 'possible' : 'impossible'