class Pile_Entier:
    def __init__(self, taille =100):
        self.taille = taille
        self.pile = []

    def empiler(self, element):
        assert not self.est_Pleine()
        self.pile.append(element)

    def depiler(self):
        assert not self.est_Vide()
        return self.pile.pop()

    def sommet(self):
        return self.pile[-1]

    def est_Vide(self):
        return len(self.pile) == 0

    def est_Pleine(self):
        return len(self.pile) == self.taille

    def purger(self):
        assert not self.est_Vide()
        i = taille - 1
        while i > -1:
            self.pile.pop()
            i -= 1

    def afficher(self):
        assert not self.est_Vide()
        for i in self.pile:
           print(i)

class Calculatrice():
    def __init__(self):
        self.pile = Pile_Entier()

    def npi(self,saisie):
        saisie = saisie.split()
        print(saisie)
        op =("+-*")
        for c in saisie:
            if c not in op:
                self.pile.empiler(c)
            else:
                a = int(self.pile.depiler())
                b = int(self.pile.depiler())
                if c == "+":
                    self.pile.empiler(b+a)
                elif c == "-":
                    self.pile.empiler(b - a)
                else:
                    self.pile.empiler(b * a)

        return self.pile.depiler()


c = Calculatrice()
print(c.npi("2 3 + 4 - "))