class String
  def convert_base(from, to)
    Integer(self, from).to_s(to)  
    
  end
end


p .convert_base(10, 23) 
p .convert_base(23, 7) 
p .convert_base(7, 10) 
p .convert_base(10, 36) 
p .convert_base(15, 10)