WORST_CASE(?,O(n^1))
* Step 1: Ara WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict TRS:
            @(dd(x,xs),ys) -> dd(x,@(xs,ys))
            @(nil(),xs) -> xs
            flatten(dd(x,xs)) -> @(x,flatten(xs))
            flatten(nil()) -> nil()
        - Signature:
            {@/2,flatten/1} / {dd/2,nil/0}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {@,flatten} and constructors {dd,nil}
    + Applied Processor:
        Ara {araHeuristics = NoHeuristics, minDegree = 1, maxDegree = 2, araTimeout = 5, araRuleShifting = Nothing}
    + Details:
        Signatures used:
        ----------------
          @ :: ["A"(13) x "A"(4)] -(1)-> "A"(4)
          dd :: ["A"(13) x "A"(13)] -(13)-> "A"(13)
          dd :: ["A"(14) x "A"(14)] -(14)-> "A"(14)
          dd :: ["A"(4) x "A"(4)] -(4)-> "A"(4)
          flatten :: ["A"(14)] -(8)-> "A"(4)
          nil :: [] -(0)-> "A"(13)
          nil :: [] -(0)-> "A"(14)
          nil :: [] -(0)-> "A"(12)
        
        
        Cost-free Signatures used:
        --------------------------
        
        
        
        Base Constructor Signatures used:
        ---------------------------------
          "dd_A" :: ["A"(1) x "A"(1)] -(1)-> "A"(1)
          "nil_A" :: [] -(0)-> "A"(1)
        

WORST_CASE(?,O(n^1))