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

Ex Input:
Sentence: 'a young boy holding a piece of paper on top of a table'. Find frequency of the letter 'y'

Ex Output:
2


Ex Input:
Sentence: 'a dog sitting in the back of a truck flat bed'. Find frequency of the letter 'h'

Ex Output:
1


Ex Input:
Sentence: 'a black and white picture of a small room with a mattress on the floor'. Find frequency of the letter 'e'

Ex Output:

4