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

Ex Input:
Sentence: 'there is a sandwich with a lot of meat cut in half'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a notebook and pen are left on a park bench'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'two sheep are standing on a grassy field'. Find frequency of the letter 'o'

Ex Output:

2