# Here your code !

def solve(w, t)
    dp = {}
    dp[0] = Array.new(w.size + 1, 0)
    (1..t).each do |j|
        dp[j] = Array.new(w.size + 1, 0)
        w.each_with_index do |k, i|
            candiate = [dp[j][i], dp[j][i] + k ]
            candiate.push(dp[j - k][i] + k) if j >= k 
            candiate.reject! {|v| v > j }              
            dp[j][i + 1] = candiate.max
        end
    end
    dp[t].include?(t)
end

n = gets.to_i
w = gets.split.map(&:to_i)

total = w.inject(0, &:+)

if total.odd?
    puts "impossible"
elsif solve(w,total/2)
    puts "possible"
else
    puts "impossible"
end