Query regarding proportionate share U/s 54f

hello, we have sold our ancestral land (owner:- me my sister and father ) and invested sale proceeds in the residential flat and claiming exemption u/s 54F.

All conditions are satisfied for u/s 54F already but problem is, that, my sister and my father invested net sale consideration from sale proceeds in one residential flat and divided the agreement value of the flat by /3 as there was 3 owner for sale proceeds same goes for investment. we have split the agreement value (total value /3) but there was no option to split stamp duty + registration cost as only a one-time payment was needed to send to the revenue dept portal to pay stamp duty charges hence my father made payment.

In this case, what needs to be done, shall I include stamp duty charges + agreement charges in the account of my father and for me and my sister we pay split charges plus extra payment made towards stamp duty against our father to add that shortfall?

for example:- residential flat value is 90 lac. 

Per assese cost is 30 lac 

stamp duty + registration charges were 5lac60k

so per asssesse charges comes @ 31 lac 86K rs 

OR 

I and my sister pay 32lac80k each 

and father paid 5lac60k + his (reduced share of aggremnt value) + 27 lac 20 thousand.

Thanks pls reply.