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

Ex Input:
Sentence: 'a woman at a table checking her cell phone'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a small white dog looking out a car window'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'groups of bananas rest on the table with pineapples behind them'. Find frequency of the letter 'd'

Ex Output:

1