DEF/00 n a:00 b:00
    IF a
        GIVE ~~b
    ELSE
        GIVE 00
DEF/00 o a:00 b:00
    IF a
        GIVE 01
    ELSE
        GIVE ~~b
SET b1:\0
IN b1
SET b0:\0
IN b0
SET a:00
a . o(a,n(b1='1,b0='1))
IF a
    OUT '1
ELSE
    OUT '0
