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: 'two people are riding on canoes down a river'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'some people on some skis in the snow'. Find frequency of the letter 'l'

Ex Output:

1