http://lcm.csa.iisc.ernet.in/dsa/node210.html
Look at the above link on how algo works.
Lets consider there are 'K' buckets (as given).
Now, for each digit you repeat the following:
1) place the digit of each number in the appropriate bin. - ø($n$)
2) append all the 'K' bins sequentially.
Thus, for a single digit, its ø($n + k$),
For 'd' digits, its ø($d(n + k)$)