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

Ex Input:
Sentence: 'a large grass pasture land with sheep grazing on grass'. Find frequency of the letter 'a'

Ex Output:
7


Ex Input:
Sentence: 'an old glass vase containing flowers on a glass table'. Find frequency of the letter 'b'

Ex Output:
1


Ex Input:
Sentence: 'a car and some people with umbrellas and a building'. Find frequency of the letter 'h'

Ex Output:

1