# http://yukicoder.me/problems/19

n = $stdin.gets.chomp.to_i
w = $stdin.gets.chomp.split(/ /).map(&:to_i).sort
dp = Array.new( n ){ Array.new() }
sum = w.inject( :+ )

if sum % 2 == 1
	puts "impossible"
	exit
else
	sum2 = sum / 2	

	0.upto( n - 1 ){ |i|
		val = w[ i ]

		dp[ i ] = dp[ i - 1].dup
		dp[ i ] << val
		dp[ i - 1 ].each{ |e|
			dp[ i ] << ( e + val )
		}

		dp[ i ].uniq! if dp[ i ].uniq
		dp[ i ].sort!

		dp[ i ].each{ |e|
			if e == sum2
				puts "possible"
				exit
			end
		}
	}
	puts "impossible"
end