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

Ex Input:
Sentence: 'a person holding onto a pink kite at the beach'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a plastic container next to a toilet on a wooden box'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'an all white horse standing in an enclosure'. Find frequency of the letter 'e'

Ex Output:

4