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

Ex Input:
Sentence: 'wooden and black bench on the side of the road'. Find frequency of the letter 'a'

Ex Output:
3


Ex Input:
Sentence: 'two people in a snowy place near a wooden fence'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'some people are standing on a crowd crowded sidewalk'. Find frequency of the letter 'r'

Ex Output:

3