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

Ex Input:
Sentence: 'a plastic plastic plate topped with three different type of food'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'a group of three dogs laying on a kitchen floor'. Find frequency of the letter 'r'

Ex Output:
3


Ex Input:
Sentence: 'a break room with a sink and a microwave'. Find frequency of the letter 'm'

Ex Output:

2