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

Ex Input:
Sentence: 'a crowd of people skiing and enjoying the snow'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a small dog sits in the rear window of a car'. Find frequency of the letter 'm'

Ex Output:
1


Ex Input:
Sentence: 'a man is riding a small motor bike'. Find frequency of the letter 'i'

Ex Output:

4