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

Ex Input:
Sentence: 'a woman sitting in front of a giant slice of cheese pizza'. Find frequency of the letter 'e'

Ex Output:
4


Ex Input:
Sentence: 'a man serving himself pizza in a wooden booth'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'people are getting on the train at the station'. Find frequency of the letter 'e'

Ex Output:

6


