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

Ex Input:
Sentence: 'a couple of items that are on the wall'. Find frequency of the letter 'm'

Ex Output:
1


Ex Input:
Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'a plate of oranges and food on a table'. Find frequency of the letter 'a'

Ex Output:

6