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

Ex Input:
Sentence: 'a white toilet sitting next to a toilet paper roller'. Find frequency of the letter 'o'

Ex Output:
4


Ex Input:
Sentence: 'a little boy standing near a couch and a table'. Find frequency of the letter 'i'

Ex Output:
2


Ex Input:
Sentence: 'a motorcycle parked next to a farm inside of a wired fence'. Find frequency of the letter 'o'

Ex Output:

4