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

Ex Input:
Sentence: 'a toilet sits in a cluttered bathroom next to a sink'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a group of giraffes walk together by a hill'. Find frequency of the letter 'b'

Ex Output:
1


Ex Input:
Sentence: 'two men and woman eating and working on laptops'. Find frequency of the letter 'i'

Ex Output:

2