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

Ex Input:
Sentence: 'some food on plates next to each other on a table'. Find frequency of the letter 'e'

Ex Output:
6


Ex Input:
Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'several different items that may have come out of a woman's purse'. Find frequency of the letter 'n'

Ex Output:

2