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

Ex Input:
Sentence: 'a construction sign is displayed on a street'. Find frequency of the letter 'i'

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: 'two boxes filled with donuts on top of a table'. Find frequency of the letter 't'

Ex Output:

5