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

Ex Input:
Sentence: 'a man holding a frisbee high into the air'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a baseball themed birthday cake is on a serving tray'. Find frequency of the letter 'g'

Ex Output:
1


Ex Input:
Sentence: 'a lady holding a glass of wine and a man holding a beer'. Find frequency of the letter 'i'

Ex Output:

3