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

Ex Input:
Sentence: 'a red building with a crowd of people outside it near the water'. Find frequency of the letter 'e'

Ex Output:
7


Ex Input:
Sentence: 'a bathroom with a sink, counter top, and mirror is shown'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'the green fire hydrant is sitting on the side of the street'. Find frequency of the letter 't'

Ex Output:

8