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

Ex Input:
Sentence: 'a boy catching a frisbee while standing ins bunch of leaves'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a airplane view of a big factory some people and cars'. Find frequency of the letter 'f'

Ex Output:
2


Ex Input:
Sentence: 'two computer screens sit on a small desk'. Find frequency of the letter 'e'

Ex Output:

4