@n = gets.strip.to_i
@w = gets.strip.split(' ').map(&:to_i)
@total = @w.inject(:+)
@w.sort!

def dfs(i, sum)
	if sum * 2 == @total
		puts "possible"
		exit
	end
	if i >= @n || sum * 2 > @total
		return
	end

	dfs(i + 1, sum)
	dfs(i + 1, sum + @w[i])
end

dfs(1, @w[0])
puts "impossible"