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

Ex Input:
Sentence: 'a red train traveling down train tracks near a forest'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a photo of a couple of people at a convention'. Find frequency of the letter 'v'

Ex Output:
1


Ex Input:
Sentence: 'a man trying to get a little girl on a boat'. Find frequency of the letter 't'

Ex Output:

6