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

Ex Input:
Sentence: 'black and white photograph of man and woman sitting on a bench'. Find frequency of the letter 'w'

Ex Output:
2


Ex Input:
Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

Ex Output:
7


Ex Input:
Sentence: 'one baseball player tackling another baseball player on the field'. Find frequency of the letter 'f'

Ex Output:

1