Original COA for the purpose of computing LTCG U/s 112A

we have purchased equity shares of one company long back on 2002 , and bonus shares were issued and subdivision into 2 shares happened... thereafter no purchase has been made , now my query is ,On sale of shares in Fy 2020-21, what can I take original COA ,can I use weighted average method or FIFO for computing ORIGINAL COA.

THANKS IN ADVANCE