CGT on gifted shares

[Jayjay123]

My parents are planning to transfer ownership of some shares to me as a gift.
If I sell the shares, how is CGT calculated?

Since I paid nothing for them, is the whole of the sell price considered profit?
OR is CGT calculated on
a) the price my parents bought them for
b) OR the market value when they are gifted to me?

Thanks for your help.

[maths]

Parents have a CGT charge based on difference between original cost and market value at date of gift.

You, on a subsequent sale, have a CGT charge based on market value at date of sale less market value at date of gift.