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

Ex Input:
Sentence: 'a flock of sheep grazing in a park'. Find frequency of the letter 'f'

Ex Output:
2


Ex Input:
Sentence: 'man riding a skate board down the little board way'. Find frequency of the letter 'k'

Ex Output:
1


Ex Input:
Sentence: 'a large clock on the wall of a building over a bench'. Find frequency of the letter 'f'

Ex Output:

1