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: 'a large motorcycle that has a man dressed in old clothing next to it'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'the street crowd is headed to the winter event'. Find frequency of the letter 't'

Ex Output:

7