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

Ex Input:
Sentence: 'a woman and a child walking down a street with a kite'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a woman throwing a frisbee on a field'. Find frequency of the letter 's'

Ex Output:
1


Ex Input:
Sentence: 'clean kitchen with plain white sink near wouldn't counter'. Find frequency of the letter 't'

Ex Output:

5