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

Ex Input:
Sentence: 'a bunch of broken down trains sit in a yard'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'a very big nice looking living room with nice furnishings'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a man sitting on a post on a sidewalk'. Find frequency of the letter 'l'

Ex Output:

1