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

Ex Input:
Sentence: 'a man makes some cock tales at a desk'. Find frequency of the letter 'k'

Ex Output:
3


Ex Input:
Sentence: 'a man in a sweatshirt is taking his own picture'. Find frequency of the letter 'u'

Ex Output:
1


Ex Input:
Sentence: 'a pizza sits on a cooling rack to cool'. Find frequency of the letter 'o'

Ex Output:

6