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

Ex Input:
Sentence: 'a bus is driving on the street behind some cars'. Find frequency of the letter 'a'

Ex Output:
2


Ex Input:
Sentence: 'a man on a skateboard going down a ramp while people are watching'. Find frequency of the letter 'w'

Ex Output:
3


Ex Input:
Sentence: 'a couple are getting dressed up for a wedding'. Find frequency of the letter 'e'

Ex Output:

6