$n = gets.to_i
$w = gets.split.map(&:to_i)
$nerai = $w.inject(:+)/2.0

$dp = Array.new($n){Array.new(100*100+1, nil)}
def dfs(depth, total)
  if depth >= $n - 1
    return total + $w[depth] if total + $w[depth] == $nerai
    return total if total == $nerai
    return -1
  end

  $dp[depth+1][total+$w[depth]] = dfs(depth+1, total+$w[depth]) if $dp[depth+1][total+$w[depth]].nil?
  $dp[depth+1][total] = dfs(depth+1, total) if $dp[depth+1][total].nil?

  return $dp[depth+1][total+$w[depth]] if $nerai == $dp[depth+1][total+$w[depth]]
  return $dp[depth+1][total] if $nerai == $dp[depth+1][total]
  return -1
end

puts dfs(-1, 0) > 0 ? "possible" : "impossible"