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

Ex Input:
Sentence: 'a flock of sheep grazing in a park'. Find frequency of the letter 'f'

Ex Output:
2


Ex Input:
Sentence: 'three birds are sitting on a tree in a forest'. Find frequency of the letter 'h'

Ex Output:
1


Ex Input:
Sentence: 'a plate that has bread and berries on it'. Find frequency of the letter 'r'

Ex Output:

3