Build a string representing a capital letter C of a given size out of 'C' characters.
generate_C(1) should return this string:
CCCCC
C
C
C
CCCCC
generate_C(2) should be
CCCCCCCCCC
CCCCCCCCCC
CC
CC
CC
CC
CC
CC
CCCCCCCCCC
CCCCCCCCCC
and so on. The string returned by generate_C(size) should have 5*size lines, following the format above. size is a positive
integer ≤ 2000.
Note that extra spaces after the C's in any line are incorrect. And the last line should not terminate with "\n".