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: 'a group of men standing around a table cutting a cake'. Find frequency of the letter 'g'

Ex Output:
3


Ex Input:
Sentence: 'a group of dogs standing outside of a screen door'. Find frequency of the letter 'o'

Ex Output:

7