Merge pull request #6 from Wizmann/master

add e11 to e20
solution of No.17 in C

他那个论坛还会删代码啊.. 代码都没了..TAT.... 这个是从聊天记录里扒出来的, 没达到两行标准
Merge pull request #7 from simonmysun/master

solution of No.17 in C
add e11.lisp
add e12.lisp
add e13.lisp
Merge pull request #9 from Z-Shang/master

add e11.lisp, e12.lisp, e13.lisp
add e21 to e29