require 'pp'

def main
  n = gets.to_i
  ws = gets.strip.split(' ').map{|e| e.to_i}
  sum = ws.reduce(:+)
  result = solve(ws, 0, sum)
  puts result ? "possible" : "impossible"
end

def solve(ws, acc, sum)
  if (sum % 2 === 1)
    return false
  end
  if (acc * 2 === sum)
    return true
  end
  if (ws.empty?)
    return false
  end
  nex = ws[0]
  _ws = ws[1..-1]
  solve(_ws, acc + nex, sum) || solve(_ws, acc, sum)
end

main()