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

Ex Input:
Sentence: 'a tower with some bright lights and clocks on it'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'a plate of food, with broccoli and nuts'. Find frequency of the letter 'b'

Ex Output:
1


Ex Input:
Sentence: 'a row of red boats next to pier with bridge in background'. Find frequency of the letter 'e'

Ex Output:

4