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

Ex Input:
Sentence: 'apples, pears, and oranges are piled up for sale'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'slices of orange are arranged on a plate'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a room attached to a kitchen that contains a computer and a tv'. Find frequency of the letter 'e'

Ex Output:

3