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

Ex Input:
Sentence: 'a man hits a tennis ball with a racket on the court'. Find frequency of the letter 'c'

Ex Output:
2


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: 'there are some sheep grazing in a field'. Find frequency of the letter 'd'

Ex Output:

1