(VAR u v x y z )
(RULES 
        admit(x, nil) -> nil
        admit(x, .(u, .(v, .(w, z)))) -> cond(=(sum(x, u, v), w), .(u, .(v, .(w, admit(carry(x, u, v), z)))))
        cond(true, y) -> y
        
)