http://acm.pku.edu.cn/JudgeOnline/problem?id=1423
! n-= (loglO (sqrt (4.0 * ACOS (0.0) * n-)) + n-* (loglO (n-) -log10 (exp (1.0))) + 1);
n-1, except ==
! n-= (loglO (sqrt (4.0 * ACOS (0.0) * n-)) + n-* (loglO (n-) -log10 (exp (1.0))) + 1);
n-1, except ==
Reproduced in: https: //my.oschina.net/garyun/blog/602856