(VAR x y )
(STRATEGY INNERMOST)
(RULES 
        -(x,0) -> x
        -(s(x),s(y)) -> -(x,y)
        min(x,0) -> 0
        min(0,y) -> 0
        min(s(x),s(y)) -> s(min(x,y))
        twice(0) -> 0
        twice(s(x)) -> s(s(twice(x)))
        f(s(x),s(y)) -> f(-(y,min(x,y)),s(twice(min(x,y))))
        f(s(x),s(y)) -> f(-(x,min(x,y)),s(twice(min(x,y))))
        
)