CMDs = ["add", "sub", "mul", "div"]


def add(self, operand):
    self.registers[int(operand[0])] += self.registers[int(operand[1])]


def sub(self, operand):
    self.registers[int(operand[0])] -= self.registers[int(operand[1])]


def mul(self, operand):
    self.registers[int(operand[0])] *= self.registers[int(operand[1])]


def div(self, operand):
    if self.registers[int(operand[1])] != 0:
        self.registers[int(operand[0])] //= self.registers[int(operand[1])]
    else:
        raise ZeroDivisionError()