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

Ex Input:
Sentence: 'a long row of tables displaying lots of fruit'. Find frequency of the letter 'o'

Ex Output:
5


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: 'there are large clay pots drying in an art studio'. Find frequency of the letter 's'

Ex Output:

2