An unsatisfiable formula is:
Channels: CBS, FOX, ACCN, Big Ten Network, CBSSN, ESPN, ESPN2, ESPNU, ESPNews, FS1, FS2, SEC Network, TBS, TNT, truTV, The CW, USA Network，详情可参考WPS下载最新地址
高速扩张与现实挑战交织，成为麦当劳中国当前最鲜明的发展特征。，更多细节参见同城约会
// Hash computation is fast