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

Ex Input:
Sentence: 'a fluffy white car looking in a mirror'. Find frequency of the letter 'k'

Ex Output:
1


Ex Input:
Sentence: 'young boy flying kite in large field at outdoor event'. Find frequency of the letter 'y'

Ex Output:
3


Ex Input:
Sentence: 'a used knife rests beside chopped carrots and minced rutabagas'. Find frequency of the letter 't'

Ex Output:

3