Decoding and Expanding Strings

  1. Read a string of interleaving digits and alphabets, while the first character is always a digit, and the ending character is always an alphabet [A-Za-z].
  2. For each group of <digit><alphabet>, this program will expand it by repeating a number of the same alphabet, as specified by the digit.
  3. For example, "1A2B" will be expanded to "ABB", while "3q" will be expanded as "qqq".
Your program may run as follows: 

Please input a string (e.g. "1A2B") -- 1A2B
ABB



Please input a string (e.g. "1A2B") -- 3q
qqq



Please input a string (e.g. "1A2B") -- 4Q593K7R
QQQQ99999KKKRRRRRRR