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

Ex Input:
Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Ex Output:
2


Ex Input:
Sentence: 'a cat sleeping near lots of pairs of shoes'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'a bus parked on the side of the road'. Find frequency of the letter 'f'

Ex Output:

1