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

Ex Input:
Sentence: 'black and white photograph of man and woman sitting on a bench'. Find frequency of the letter 'w'

Ex Output:
2


Ex Input:
Sentence: 'a bed with a mattress that has nothing on it'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a man at a park eating something like a hotdog'. Find frequency of the letter 't'

Ex Output:

4