(VAR k l x y z )
(STRATEGY INNERMOST)
(RULES 
        app(nil,k) -> k
        app(l,nil) -> l
        app(cons(x,l),k) -> cons(x,app(l,k))
        sum(cons(x,nil)) -> cons(x,nil)
        sum(cons(x,cons(y,l))) -> sum(cons(a(x,y,h),l))
        a(h,h,x) -> s(x)
        a(x,s(y),h) -> a(x,y,s(h))
        a(x,s(y),s(z)) -> a(x,y,a(x,s(y),z))
        a(s(x),h,z) -> a(x,z,z)
        
)