(VAR x y z )
(STRATEGY INNERMOST)
(RULES 
        min(x,0) -> 0
        min(0,y) -> 0
        min(s(x),s(y)) -> s(min(x,y))
        max(x,0) -> x
        max(0,y) -> y
        max(s(x),s(y)) -> s(max(x,y))
        -(x,0) -> x
        -(s(x),s(y)) -> -(x,y)
        gcd(s(x),s(y),z) -> gcd(-(max(x,y),min(x,y)),s(min(x,y)),z)
        gcd(x,s(y),s(z)) -> gcd(x,-(max(y,z),min(y,z)),s(min(y,z)))
        gcd(s(x),y,s(z)) -> gcd(-(max(x,z),min(x,z)),y,s(min(x,z)))
        gcd(x,0,0) -> x
        gcd(0,y,0) -> y
        gcd(0,0,z) -> z
        
)