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

Ex Input:
Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Ex Output:
2


Ex Input:
Sentence: 'a young woman dressed in green and black operating a remote control'. Find frequency of the letter 'r'

Ex Output:
5


Ex Input:
Sentence: 'this is a picture of a man standing on a street'. Find frequency of the letter 'h'

Ex Output:

1