fun(1,4)--->fun(2,4) --->fun(3,4)--->fun(4,4)*
--->fun(4,5)*
--->fun(4,6)*
--->fun(4,4)*
--->fun(3,4) --->fun(4,4)*
--->fun(4,6...
------------------------------------------------------
fun(2,4) --->fun(3,4)--->fun(4,4)*
-------------------------------------------------------
fun(3,4) --->fun(4,4)*
-阿摩線上測驗