def main()
    n = gets.to_i
    w = gets.split(" ").map{|a| a.to_i}

    if w.sum % 2 != 0
        puts "impossible"
        return
    end

    a = Array.new(11000, 0)
    a[w[0]] = 1
    for i in 1...n
        for j in 0...(a.length)
            if a[j] == 1
                a[w[i] + j] = 1
            end
        end
        a[w[i]] = 1
    end
    if a[w.sum/2] == 1
        puts "possible"
    else
        puts "impossible"
    end
end

main()