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

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: 'a pizza pie sitting on a wooden table with tongs'. Find frequency of the letter 't'

Ex Output:
5


Ex Input:
Sentence: 'three people outside posing for a picture with a white frisbee'. Find frequency of the letter 'u'

Ex Output:

2