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

Ex Input:
Sentence: 'two women standing next to each other holding tennis rackets'. Find frequency of the letter 't'

Ex Output:
7


Ex Input:
Sentence: 'the street sign is next to a curved road'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'dog in the air to catch a frisbee while a man lays on the ground'. Find frequency of the letter 'a'

Ex Output:

6