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

Ex Input:
Sentence: 'a woman walking on a shore next to a river'. Find frequency of the letter 'v'

Ex Output:
1


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 dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Ex Output:

2