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

Ex Input:
Sentence: 'an audience watches as a bird spreads its wings'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a group of workers washing and cleaning fruits and vegetables'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a large group of people riding motorcycles down a city street'. Find frequency of the letter 'g'

Ex Output:

3