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

Ex Input:
Sentence: 'older man getting ready to swing his bat at a ball on a stand in front of a group of viewers'. Find frequency of the letter 'n'

Ex Output:
7


Ex Input:
Sentence: 'a man holding a baseball bat an playing baseball'. Find frequency of the letter 'l'

Ex Output:
6


Ex Input:
Sentence: 'a group of animals laying in between two groves of trees'. Find frequency of the letter 'w'

Ex Output:

2