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

Ex Input:
Sentence: 'decorated baseball cake in a clear plastic box'. Find frequency of the letter 'k'

Ex Output:
1


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: 'several bicycles are parked next to the window of a brown brick building that has flower boxes on the window'. Find frequency of the letter 'n'

Ex Output:

6