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

Ex Input:
Sentence: 'an empty clean kitchen with island, marble countertops , stove and cabinetry'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'statues of 2 zebras and 1 giraffe in a doorway'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'a bunch of fruit sitting in a bowl, its overflowing'. Find frequency of the letter 't'

Ex Output:

4