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

Ex Input:
Sentence: 'a train sits on a railroad track as a metal awning covers it'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'a bowl of granola with raspberries and honey on top with a spoon'. Find frequency of the letter 'w'

Ex Output:
3


Ex Input:
Sentence: 'a couple is riding a motorcycle that is pulling a cart behind it'. Find frequency of the letter 'y'

Ex Output:

1