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

Ex Input:
Sentence: 'children with scissors and construction paper in a school classroom'. Find frequency of the letter 'c'

Ex Output:
6


Ex Input:
Sentence: 'a small white dog looking out a car window'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'a giraffe sticking out is tongue to grasp an item from a person's hand'. Find frequency of the letter 's'

Ex Output:

5