我有一个list如下结构：
L =["ticket1","ticket2","spec1","spec2",
"ticket3","ticket4","spec3",
"ticket5","spec4","spec5",
"ticket6","ticket7","ticket8",
"ticket9","ticket10","spec6","spec7",
"ticket11","ticket12",
"ticket13","spec8",
"ticket14","spec9"]

想要挑出来后面没有跟着spec的ticket，具体规则如下：
1.如果连续两个ticket后面跟着连续两个spec，那么这两个ticket算有spec，如ticket1，ticket2;ticket9,ticket10
2.如果一个ticket后面跟着一个或者连续多个spec,那么这个ticket也算有spec，如ticket4,ticket5,ticket13,ticket14;

剩下的ticket都算是没有spec的，我想要挑出这些ticket，有哪些好的方法可以使用呀？
没有spec的ticket如下：ticket3,ticket6,ticket7,ticket8,ticket11,ticket12

列表里面的信息是唯一的信息，请教各位大神有什么方法可以实现这样的挑选。