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

Ex Input:
Sentence: 'a woman cross country skiing in a competition'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'there is a zebra that is walking enar a car'. Find frequency of the letter 'r'

Ex Output:
4


Ex Input:
Sentence: 'bottles of booze sit in the background behind a sandwich and a bit of beets'. Find frequency of the letter 'd'

Ex Output:

4