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

Ex Input:
Sentence: 'a large motorcycle that has a man dressed in old clothing next to it'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'a person is performing a stunt on a snowboard'. Find frequency of the letter 'p'

Ex Output:
2


Ex Input:
Sentence: 'a clock on a wall and a light fixture on a ceiling'. Find frequency of the letter 'i'

Ex Output:

4