In this task, you need to count the number of times the given letter appears in the given sentence.

Ex Input:
Sentence: 'a baseball player dropping his bat and starting to run'. Find frequency of the letter 'o'

Ex Output:
2


Ex Input:
Sentence: 'a large motorcycle that has a man dressed in old clothing next to it'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'small kitchen area with sink full of dirty dishes'. Find frequency of the letter 'l'

Ex Output:

4