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 row of vintage cars in a grassy field'. Find frequency of the letter 'v'

Ex Output:
1


Ex Input:
Sentence: 'a beautiful red and green bird standing on a bowl of food'. Find frequency of the letter 'd'

Ex Output:

5