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

Ex Input:
Sentence: 'a group of people are playing soccer on a beach'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'the street sign is next to a curved road'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'people in a bakery buying donuts and other selling'. Find frequency of the letter 'b'

Ex Output:

2