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: 'a sailboat is floating near the rocky shore of a beach'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a young couple and their two children enjoy a relaxing meal in a floating cabana'. Find frequency of the letter 'g'

Ex Output:

3