class TaulerSE:

    def __init__(self, nc):
        self.ncaselles = nc
        self.__se = {}

    def nombre_se(self):
        return len(self.__se)

    def __getitem__(self, i):
        if i in self.__se:
            return self.__se[i]
        else:
            return 0

    def afegir_escala(self, ci, cf):
        self.__se[ci] = cf
        
    def afegir_serp(self, ci, cf):
        self.__se[cf] = ci