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: 'a sheep in a field in front of other sheep'. Find frequency of the letter 'f'

Ex Output:
3


Ex Input:
Sentence: 'a man with a surf board among the waves'. Find frequency of the letter 'w'

Ex Output:

2