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

Ex Input:
Sentence: 'a bird in a tree looking up at branches'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a small white plane sitting on top of the ocean'. Find frequency of the letter 'e'

Ex Output:
4


Ex Input:
Sentence: 'two glazed doughnuts in a see through pastry bag'. Find frequency of the letter 'g'

Ex Output:

4