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

Ex Input:
Sentence: 'a person trying to flip a skateboard in a garage'. Find frequency of the letter 'a'

Ex Output:
7


Ex Input:
Sentence: 'a man using a video game controller in a room'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a giraffe licks the side of the building'. Find frequency of the letter 'd'

Ex Output:

2