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

Ex Input:
Sentence: 'a row of vintage cars in a grassy field'. Find frequency of the letter 'v'

Ex Output:
1


Ex Input:
Sentence: 'a photo of a couple of people at a convention'. Find frequency of the letter 'v'

Ex Output:
1


Ex Input:
Sentence: 'a young lady driving a large vehicle is unaware her picture is being taken'. Find frequency of the letter 'i'

Ex Output:

7