10
{
    65
    digit-left
    @0
    111
    dup
    digits
    64
    power-of-10
    base #(list to num)
    *
    *
    digits
        1
        =
    m2
    10
    base #(list to num)
    +
}
31
times #(eval)
digits
( " XX" )
select
64
chunks
    init
m1
unlines