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

Ex Input:
Sentence: 'a bunch of people are standing out in a field a red one has their arms out as a white ball is in the air'. Find frequency of the letter 'e'

Ex Output:
9


Ex Input:
Sentence: 'a woman holds some baked goods at the convention'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a row of people in a larger audience watching something'. Find frequency of the letter 'p'

Ex Output:

2