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

Ex Input:
Sentence: 'a blue fire hydrant painted on the bottom of it'. Find frequency of the letter 'h'

Ex Output:
2


Ex Input:
Sentence: 'a man skating down a stair rail in front of a bunch of people'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'an elephant is pulling on a large cart'. Find frequency of the letter 'g'

Ex Output:

2