Decoding input string - so called task of 'decompression'

[1] Valentyn N Sichkar. Decoding string, decompression task // GitHub platform [Electronic resource]. URL: https://github.com/sichkar-valentyn/String_Decoding (date of access: XX.XX.XXXX)

Program decode string implementing so called task of decompression.
For example input string is 3a5Ba4CcF3f and resulted decompressed string is aaaBBBBBaCCCCcFfff.

[1] Valentyn N Sichkar. Decoding string, decompression task // GitHub platform [Electronic resource]. URL: https://github.com/sichkar-valentyn/String_Decoding (date of access: XX.XX.XXXX)