def corrent_format?(str)
  i = 0
  if str.length%2 == 0
    while i < str.length  do
      puts "#{get_opp(str[i])} ... #{str[i]} ... #{str[i+1]}"
      if(get_opp(str[i]) && get_opp(str[i]) == str[i+1])
        if(str.length == 2)
          return true
        else
          new_str = str[0..(i-1)] + str[(i+1)..str.length]
          return corrent_format?(new_str)
        end
      else
        return false
      end
    end
  else
    return false
  end
end


corrent_format?("[()()]")