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

Ex Input:
Sentence: 'a player swings his bat at a baseball game'. Find frequency of the letter 'p'

Ex Output:
1


Ex Input:
Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'stopped tour bus with tourists exploring large rocks along mountainside road'. Find frequency of the letter 'd'

Ex Output:

3