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

Ex Input:
Sentence: 'there is a stop sign that has a reflection in a puddle'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a kitchen with hanging lights, an island with sink and bar stools, a refrigerator, small pantry door, wooden cabinets and shiny wood floor'. Find frequency of the letter 'n'

Ex Output:
12


Ex Input:
Sentence: 'a man riding a skateboard down the middle of a street'. Find frequency of the letter 'a'

Ex Output:

6