ac = ac + (-1 << approxBit);
ac += -1 << approxBit;
int refineAC(int ac, int approxBit) {	if (ac > 0) {		int bit = nextBit();		if (bit != 0) {			ac = ac + (1 << approxBit);		}	} else if (ac < 0) {		int bit = nextBit();		if (bit != 0) {			ac = ac + (-1 << approxBit);		}	}	return ac;}