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

Ex Input:
Sentence: 'a display case filled with lots of different clocks'. Find frequency of the letter 'w'

Ex Output:
1


Ex Input:
Sentence: 'a large bathroom with marble floor, counter, and bath'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a woman at work smiling from behind a counter'. Find frequency of the letter 'r'

Ex Output:

3