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

Ex Input:
Sentence: 'a bowl of vegetables in a soup like substance next to a spoon'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'a room filled with furniture and a tv'. Find frequency of the letter 'a'

Ex Output:

3