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

Ex Input:
Sentence: 'a airplane view of a big factory some people and cars'. Find frequency of the letter 'f'

Ex Output:
2


Ex Input:
Sentence: 'a person with some scissors over a bowl'. Find frequency of the letter 's'

Ex Output:
6


Ex Input:
Sentence: 'a red bus is near a curb on a brick road near a lane of shops'. Find frequency of the letter 'b'

Ex Output:

3