Vlookup

trying to explain this may tough, we have a speadsheet with 12k rows and 8k unique accounts numbers. We are assigning a rank to these account numbers
The problem we are having is many of these are accounts are the same account number all in column A, and rank is in B... But we may have the same rank for differnt acount numbers... instead of all the copying and pasting does anyone have an idea for a formula that may work to solve this, so as long as I rank one of the accounts it will duplicate its rank all the way down the columns. your help would be much aprreaciated
So i will have to rank 8k accounts individually, which is fine, i just need it to repeat itself if there are duplicate account numbers...which there are 4k duplicates

account rank
1234 1
1256 2
1234 1
1298 1
1234 1
1298 1
1256 2
1865 3
1865 3
1865 3
1234 1
1234 1
1298 1