Number series ending 50 and 100

[Marcia]

Hi all. I would like help with a formula that returns the last number of an invoice booklet in B2. The invoice booklets are bound in 50 pcs per book.
If number 6387127 is entered in A2, the formula in B2 should return 6387150. If the number in A3 is 6387079, B3 should be 6387100.


I tried extracting the last two numbers using the Right function but it converted the result to text with error results.
Sample data attached. Thank you.