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

Ex Input:
Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'a family sitting at a table in a restaurant looking at their phones'. Find frequency of the letter 't'

Ex Output:
8


Ex Input:
Sentence: 'an empty grocery area with several trash and recycling containers'. Find frequency of the letter 'c'

Ex Output:

4