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

Ex Input:
Sentence: 'a picture of a toilet and toilet paper in a bathroom'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'men are riding on motorcycles with a man riding in their carriers'. Find frequency of the letter 'r'

Ex Output:
8


Ex Input:
Sentence: 'a woman with red hair and a hat with flashlights on it'. Find frequency of the letter 'w'

Ex Output:

3