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

Ex Input:
Sentence: 'a social occasion of people are uncovered before the open day'. Find frequency of the letter 'c'

Ex Output:
4


Ex Input:
Sentence: 'a plastic tray that has different foods inside of it'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a room with decorations on a shelf and a painting on the wall'. Find frequency of the letter 'n'

Ex Output:

6