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

Ex Input:
Sentence: 'a river with a long dragon boat in it and rowers on the boat in sets of two, along with two other people'. Find frequency of the letter 'h'

Ex Output:
4


Ex Input:
Sentence: 'a toilet sits in a cluttered bathroom next to a sink'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'an image of tour bus going down the road'. Find frequency of the letter 'f'

Ex Output:

1