class nBit:
    def __init__(self, bitlength):
        self.bitlength = bitlength
        self.registers = {"a": 0}
        self.carry_status = 0

    def create_register(self, name):
        self.registers[name] = 0

    def set_register(self, name, v):
        self.check(v)
        self.registers[name] = v

    def get_register(self, name):
        return self.registers[name]

    def check(self, n):
        if n.bitlength > self.bitlength:
            raise OverflowError

    def maybe_carry(self):
        if self.registers["a"].bit_length() > self.bitlength:
            self.registers["a"] &= 1 << self.bitlength - 1
            self.carry_status

    def add(self, v):
        self.registers["a"] += v
        self.maybe_carry()

    def shift_right(self):
        self.registers["a"] >>= 1
        if self.carry_status == 1:
            self.registers["a"] &= 1 << self.carry_status

    def shift_left(self):
        self.registers["a"] <<= 1
        self.maybe_carry()