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

Ex Input:
Sentence: 'a man with a skateboard that is in the street'. Find frequency of the letter 'o'

Ex Output:
1


Ex Input:
Sentence: 'a man serving himself pizza in a wooden booth'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a small child in a gray hoodie eating a doughnut'. Find frequency of the letter 'o'

Ex Output:

3