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

Ex Input:
Sentence: 'a piece of bread stuffed with meat and vegetables'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a couple of men sitting next to each other under an umbrella'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'a stop sign gives directions to travelers on a gray, snowy day'. Find frequency of the letter 'i'

Ex Output:

4