WORST_CASE(?,O(n^2))
* Step 1: NaturalPI WORST_CASE(?,O(n^2))
    + Considered Problem:
        - Strict TRS:
            +(x,0()) -> x
            +(x,s(y)) -> s(+(x,y))
            sum(0()) -> 0()
            sum(s(x)) -> +(sum(x),s(x))
        - Signature:
            {+/2,sum/1} / {0/0,s/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {+,sum} and constructors {0,s}
    + Applied Processor:
        NaturalPI {shape = Quadratic, restrict = NoRestrict, uargs = UArgs, urules = URules, selector = Nothing}
    + Details:
        We apply a polynomial interpretation of kind constructor-based(quadratic):
        The following argument positions are considered usable:
          uargs(+) = {1},
          uargs(s) = {1}
        
        Following symbols are considered usable:
          {+,sum}
        TcT has computed the following interpretation:
            p(+) = 4 + x1 + 2*x2
            p(0) = 2            
            p(s) = 2 + x1       
          p(sum) = 3*x1 + x1^2  
        
        Following rules are strictly oriented:
         +(x,0()) = 8 + x         
                  > x             
                  = x             
        
        +(x,s(y)) = 8 + x + 2*y   
                  > 6 + x + 2*y   
                  = s(+(x,y))     
        
         sum(0()) = 10            
                  > 2             
                  = 0()           
        
        sum(s(x)) = 10 + 7*x + x^2
                  > 8 + 5*x + x^2 
                  = +(sum(x),s(x))
        
        
        Following rules are (at-least) weakly oriented:
        

WORST_CASE(?,O(n^2))