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

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

Ex Output:
3


Ex Input:
Sentence: 'a man in a suit makes the first slice into a cake'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'people eating on the street standing next to a post'. Find frequency of the letter 'e'

Ex Output:

7