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

Ex Input:
Sentence: 'a street at night with trees and streetlights on'. Find frequency of the letter 't'

Ex Output:
9


Ex Input:
Sentence: 'two computers and a laptop set up on a desk'. Find frequency of the letter 'r'

Ex Output:
1


Ex Input:
Sentence: 'a person that is playing a video game in a room here'. Find frequency of the letter 'a'

Ex Output:

6