Python 3:

Write a function CharCount, to take a string S and a single character C, and returns the count of C (one letter) in the string S. If the letter of C is not found in S, the function returns -1. You must write your own function to do this and can not use any built-in counting functions.

Use the function in main to get two inputs from the user, a sentence and a character, then show the count of that character or an error message if the count is -1.