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

Ex Input:
Sentence: 'a wedding cake with pink roses on a silver plate'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a red stop sign with street signs above it'. Find frequency of the letter 't'

Ex Output:
5


Ex Input:
Sentence: 'a woman at a table checking her cell phone'. Find frequency of the letter 'a'

Ex Output:

5