质数判断

bool IsPrime(uint64_t n) {
	bool r = (n != 1);
	if (n > 2) {
		uint64_t lm = sqrt(n);
		for (uint64_t i = 2; i <= lm; i++){
			if (n % i == 0) {
				r = false;
				break;
			}
		}
	}
	return r;
}