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

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

Ex Output:
2


Ex Input:
Sentence: 'pizza with different vegetables sitting on top of a wooden slab'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a wooden cutting board topped with a cake and cookies next to donuts'. Find frequency of the letter 'p'

Ex Output:

2