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

Ex Input:
Sentence: 'the wooden kitchen has a small child's plastic table in it'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'a red building with a crowd of people outside it near the water'. Find frequency of the letter 'e'

Ex Output:
7


Ex Input:
Sentence: 'a pretty young lady using a smart phone'. Find frequency of the letter 'y'

Ex Output:

3