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

Ex Input:
Sentence: 'the snowboarder wearing a dark helmet sprays snow into the air'. Find frequency of the letter 'w'

Ex Output:
3


Ex Input:
Sentence: 'a baseball player dropping his bat and starting to run'. Find frequency of the letter 'o'

Ex Output:
2


Ex Input:
Sentence: 'a car and a pick-up parked in front of a cafe on a one way street'. Find frequency of the letter 'c'

Ex Output:

3