n,x=gets.split.map(&:to_i)
as=gets.split.map(&:to_i).map.with_index { |a,i| [a,i] }
as.sort!
as.reverse!

ans = []
for i in 0...n
  if 0 <= x-as[i][0]
    x -= as[i][0]
    ans[as[i][1]] = true
  else
    ans[as[i][1]] = false
  end
end

if x == 0
  puts ans.map{|b|b ? 'o' : 'x'}.join ''
else
  puts "No"
end