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

Ex Input:
Sentence: 'a little boy sitting on a bed in a bedroom'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'there is a baseball game on and a few people are watching'. Find frequency of the letter 'i'

Ex Output:
2


Ex Input:
Sentence: 'a fighter jet is flying through the air'. Find frequency of the letter 'e'

Ex Output:

3