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

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 group of cows that are standing in the grass'. Find frequency of the letter 'g'

Ex Output:
3


Ex Input:
Sentence: 'there is a stop sign that has a reflection in a puddle'. Find frequency of the letter 'e'

Ex Output:

5