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 toasted sub sandwich is next to a salad'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'a clock is attached to a pipe on the ceiling'. Find frequency of the letter 'e'

Ex Output:

4