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

Ex Input:
Sentence: 'a parking meter painted green with a sign that describes it as not a parking meter'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'this is a sign in front of a large cathedral'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a dog playing with a toy in the snow'. Find frequency of the letter 'h'

Ex Output:

2