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

Ex Input:
Sentence: 'two zebra stand near the wooden posts on a building'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'a man flying through the air on top of a skateboard'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'two street signs on top of each other on a metal pole'. Find frequency of the letter 'n'

Ex Output:

3