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

Ex Input:
Sentence: 'small airplane in the process of taking off'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a picture of a toilet and toilet paper in a bathroom'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a blender on a counter top holds some food'. Find frequency of the letter 'e'

Ex Output:

4