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

Ex Input:
Sentence: 'a room with a big screen television and a couch'. Find frequency of the letter 'h'

Ex Output:
2


Ex Input:
Sentence: 'a white police vehicle parked on a paved street'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'the little girl is watching a polar bear'. Find frequency of the letter 'a'

Ex Output:

4