# 定义一个计数器类

class Counter:
    def __init__(self, init=0):
        self._count = init

    def inc(self): self._count += 1
    def dec(self): self._count -= 1
    def value(self): return self._count
    def reset(self): self._count = 0

if __name__ == '__main__':
    c = Counter()
    c.inc()
    c.inc()
    c.dec()
    print(c.value())
    c.reset()