(mod (A prev-coin-bundle B)
     (defmacro assert items
       (if (r items)
           (list if (f items) (c assert (r items)) (q . (x)))
         (f items)
         )
       )

     (defun is-valid-bundle ((X . Y) Z)
       (sha256 X Y Z)
       )

     (defun main (A prev-coin-bundle B)
       (assert
        (is-valid-bundle (+ 1 A) prev-coin-bundle B)
        (is-valid-bundle (+ 2 A) prev-coin-bundle B)
        )
       )

     (main A prev-coin-bundle B)
     )