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 social occasion of people are uncovered before the open day'. Find frequency of the letter 'c'

Ex Output:
4


Ex Input:
Sentence: 'a sandwich a pickle and some chips with soup and a drink'. Find frequency of the letter 'e'

Ex Output:

2