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

Ex Input:
Sentence: 'a cat that is standing next to an open suitcase'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a child sitting a table with a pizza in front of him'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'some people are walking down a road holding kites'. Find frequency of the letter 'r'

Ex Output:

2