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

Ex Input:
Sentence: 'a little dog on a table while a dog groomer cuts its fur'. Find frequency of the letter 'r'

Ex Output:
3


Ex Input:
Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'three propeller planes are parked inside a hangar'. Find frequency of the letter 'a'

Ex Output:

6