class CssBuilder:
    def __init__(self):
        self.css = ""

    def add_style(self, style):
        self.css += style.render()

    def get_css(self):
        return self.css

class CssStyle(ABC):
    @abstractmethod
    def render(self):
        pass

class DivStyle(CssStyle):
    def render(self):
        return "div { margin: 10px; }\n"

class LabelStyle(CssStyle):
    def render(self):
        return "label { font-size: 14px; color: #333; }\n"

class InputStyle(CssStyle):
    def render(self):
        return "input[type='text'] { padding: 5px; }\n"

class SelectStyle(CssStyle):
    def render(self):
        return "select { width: 100px; }\n"

class SubmitStyle(CssStyle):
    def render(self):
        return "input[type='submit'] { background-color: #4CAF50; color: white; }\n"