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

Ex Input:
Sentence: 'a ready to eat pizza on a rack'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'a baby elephant walks beside an adult elephant along a post and cable'. Find frequency of the letter 'l'

Ex Output:
6


Ex Input:
Sentence: 'a person riding a surf board holding a parachute'. Find frequency of the letter 'r'

Ex Output:

5