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

Ex Input:
Sentence: 'a herd of giraffes in tall african grass'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'a blue bowl holding mashed bananas and oatmeal with a bottle of sugar and cinnamon sitting beside it'. Find frequency of the letter 'g'

Ex Output:
3


Ex Input:
Sentence: 'the man looks back at people riding jet skis near a long boat'. Find frequency of the letter 'e'

Ex Output:

5