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

Ex Input:
Sentence: 'a few giraffes standing in a field looking around'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'

Ex Output:
5


Ex Input:
Sentence: 'two giraffes  against a feeding station in a stone-like enclosure'. Find frequency of the letter 'u'

Ex Output:

1