Derive a Python function named count that will calculate the number of occurrences of character c in a chain s. try 2 versions: with the method count of the str class and without that it (use a loop while or for).

Develop the main part of the program that get from the user a character chain named s, and call the function twice to calculate the number of a and of 'de la'. The last part should be:

print(count(s,'a'))