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

Ex Input:
Sentence: 'a chair and umbrella on a sandy beach'. Find frequency of the letter 's'

Ex Output:
1


Ex Input:
Sentence: 'this is a close up view of a tennis player during the game'. Find frequency of the letter 't'

Ex Output:
3


Ex Input:
Sentence: 'giraffes eating from the box set high in their zoo enclosure'. Find frequency of the letter 's'

Ex Output:

3