C++ Programming. Dont use other libraries other than iostream & using namespace std; thanks

Write a function, CountVowels, that takes a string as input and count the number of vowels (a,e,i,o,u either upper or lower case) alphabetic characters. The function returns an integer value for the number of vowels.

Your function should be named CountVowels

Your function has one input argument of type string

Your function has one return value of type integer representing the number of vowels in the input string

Your function should not print anything

Example: Calling function with a string "One1, Two2", should return 3.

Edge Cases:

If there are no vowel characters in the string, return 0

If the string is empty, return -1