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

Ex Input:
Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'

Ex Output:
5


Ex Input:
Sentence: 'a close up of a plate with a whole carrot'. Find frequency of the letter 'w'

Ex Output:
2


Ex Input:
Sentence: 'potatoes sitting underneath a bunch of bananas'. Find frequency of the letter 'n'

Ex Output:

6