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

Ex Input:
Sentence: 'a wedding cake with pink roses on a silver plate'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'a bowl of vegetables in a soup like substance next to a spoon'. Find frequency of the letter 'a'

Ex Output:
5


Ex Input:
Sentence: 'a baseball player is at bat waiting for the pitch'. Find frequency of the letter 'f'

Ex Output:

1