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

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

Ex Output:
8


Ex Input:
Sentence: 'a dilapidated bench in a park under a tree'. Find frequency of the letter 'p'

Ex Output:
2


Ex Input:
Sentence: 'a giraffe is looking at the camera with a smirk on it's face'. Find frequency of the letter 'i'

Ex Output:

6