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

Ex Input:
Sentence: 'man is snow gear and skis skiing in the snow'. Find frequency of the letter 'i'

Ex Output:
5


Ex Input:
Sentence: 'a family sitting at a table in a restaurant looking at their phones'. Find frequency of the letter 't'

Ex Output:
8


Ex Input:
Sentence: 'a female tennis player tosses a ball in the air for a serve'. Find frequency of the letter 'e'

Ex Output:

8