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

Ex Input:
Sentence: 'a laptop computer with pictures of giraffes on the homescreen'. Find frequency of the letter 'o'

Ex Output:
5


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 group of skinny cows gaze on brown grass'. Find frequency of the letter 'e'

Ex Output:

1