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

Ex Input:
Sentence: 'a herd of giraffes in tall african grass'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'people plating cake in an office meeting room'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'large white cow standing in a field by a barn'. Find frequency of the letter 'i'

Ex Output:

4