DWORD rnd(DWORD n)
{
	HCRYPTPROV p;	DWORD r;

	//乱数初期化
	CryptAcquireContext(&p, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
	//乱数生成
	CryptGenRandom(p, sizeof(r), (BYTE*)&r);
	//解放
	CryptReleaseContext(p, NULL);

	return r%n;
}