* Step 1: Sum WORST_CASE(Omega(n^1),?)
    + Considered Problem:
        - Strict TRS:
            active(b()) -> mark(a())
            active(f(X,X)) -> mark(f(a(),b()))
            active(f(X1,X2)) -> f(active(X1),X2)
            f(mark(X1),X2) -> mark(f(X1,X2))
            f(ok(X1),ok(X2)) -> ok(f(X1,X2))
            proper(a()) -> ok(a())
            proper(b()) -> ok(b())
            proper(f(X1,X2)) -> f(proper(X1),proper(X2))
            top(mark(X)) -> top(proper(X))
            top(ok(X)) -> top(active(X))
        - Signature:
            {active/1,f/2,proper/1,top/1} / {a/0,b/0,mark/1,ok/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {active,f,proper,top} and constructors {a,b,mark,ok}
    + Applied Processor:
        Sum {left = someStrategy, right = someStrategy}
    + Details:
        ()
* Step 2: DecreasingLoops WORST_CASE(Omega(n^1),?)
    + Considered Problem:
        - Strict TRS:
            active(b()) -> mark(a())
            active(f(X,X)) -> mark(f(a(),b()))
            active(f(X1,X2)) -> f(active(X1),X2)
            f(mark(X1),X2) -> mark(f(X1,X2))
            f(ok(X1),ok(X2)) -> ok(f(X1,X2))
            proper(a()) -> ok(a())
            proper(b()) -> ok(b())
            proper(f(X1,X2)) -> f(proper(X1),proper(X2))
            top(mark(X)) -> top(proper(X))
            top(ok(X)) -> top(active(X))
        - Signature:
            {active/1,f/2,proper/1,top/1} / {a/0,b/0,mark/1,ok/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {active,f,proper,top} and constructors {a,b,mark,ok}
    + Applied Processor:
        DecreasingLoops {bound = AnyLoop, narrow = 10}
    + Details:
        The system has following decreasing Loops:
          f(x,y){x -> mark(x)} =
            f(mark(x),y) ->^+ mark(f(x,y))
              = C[f(x,y) = f(x,y){}]

WORST_CASE(Omega(n^1),?)