N=gets.to_i
W=gets.split.map(&:to_i)
S=W.sum

if S%2==1
    puts "impossible"
    exit
end

DP=Array.new(11000,0)
DP[0]=1

for i in 0...N do
    for j in 10500.downto(0) do
        DP[j]=1 if 0<=j-W[i] && DP[j-W[i]]==1
    end
end

puts "possible" if DP[S/2]==1
puts "impossible" if DP[S/2]!=1