N = gets.to_i
W = gets.split.map(&:to_i)
def f(i, w)
  @dp ||= {}
  @dp[[i, w]] ||= if i == 0
                    w == 0 || w == W[0]
                  elsif w < W[i]
                    f(i - 1, w)
                  else
                    f(i - 1, w) || f(i - 1, w - W[i])
                  end
end
s = W.inject(:+)
ans = if s % 2 == 0 and f(N - 1, s / 2)
        "possible"
      else
        "impossible"
      end
puts ans