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

Ex Input:
Sentence: 'there is a woman pointing at something with her dog'. Find frequency of the letter 'i'

Ex Output:
5


Ex Input:
Sentence: 'a giraffe shares a habitat with a zebra, an ostrich, and an okapi'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'desk in the corner holding a laptop, keyboard, books and other items by the window'. Find frequency of the letter 'y'

Ex Output:

2