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

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 person on a skateboard going down a ramp'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a man is taking a picture of a man and woman'. Find frequency of the letter 'a'

Ex Output:

8