// (it isn't always in every impl)
At a national level, a survey by insurer Direct Line published in December suggested that nearly four million UK adults might be living in a home without any smoke alarm at all. In the US, an estimated 16% of households do not have a functioning smoke alarm.
，详情可参考雷电模拟器官方版本下载
The user will give a CNF in dimacs format.。业内人士推荐WPS官方版本下载作为进阶阅读
Opens in a new window
This story continues at The Next Web