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

Ex Input:
Sentence: 'the sun goes down over a bike tied to a bench at the beach'. Find frequency of the letter 't'

Ex Output:
5


Ex Input:
Sentence: 'two people are riding on canoes down a river'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a large jet liner flying through a light blue sky'. Find frequency of the letter 't'

Ex Output:

3