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

Ex Input:
Sentence: 'a lady mixes some things in a blender as people look on'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a blue tripocal bird is perched on a wooden fence'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a couple of people are sitting at a table'. Find frequency of the letter 'e'

Ex Output:

5