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

Ex Input:
Sentence: 'a few men walking through a market place'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

Ex Output:
7


Ex Input:
Sentence: 'a closet with a fan, luggage and various boxes'. Find frequency of the letter 'a'

Ex Output:

6