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: 'pedestrian in stripe clothing standing on street corner'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'a chili cheese hot dog sandwich on a paper towel'. Find frequency of the letter 'w'

Ex Output:

2