line-mode
words
        ascii-digits
        uppercase-alphabet
        catenate #(list+list)
        save-a
        index
    m5
    10
    base #(list to num)
m4
sum
dec
10
    -
    @1
    over
    0
    >=
    digit-left
b6
3
times #(eval)
4
*
+
digits
tail
push-a
tail
select