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

Ex Input:
Sentence: 'a black computer with a screen reading "press any key to begin."'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a woman fully dressed as a geisha'. Find frequency of the letter 'm'

Ex Output:
1


Ex Input:
Sentence: 'there is a white truck towing a red bus'. Find frequency of the letter 'c'

Ex Output:

1