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

Ex Input:
Sentence: 'a line of people on motorcycles on the road'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a young boy wearing black and holding a skateboard on the sidewalk'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'a bathroom with white walls and a toilet'. Find frequency of the letter 'o'

Ex Output:

3