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

Ex Input:
Sentence: 'a small boat travels on the water next to the shore'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a bus is stopped in front of a graphic statue'. Find frequency of the letter 'e'

Ex Output:
2


Ex Input:
Sentence: 'a bunch of suitcases and boxes sitting around in piles'. Find frequency of the letter 'u'

Ex Output:

3