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()