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

Ex Input:
Sentence: 'an audience watches as a bird spreads its wings'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'service men and women attending a buffet for america'. Find frequency of the letter 'f'

Ex Output:

3