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

Ex Input:
Sentence: 'a toilet of some sort near a sink of some sort'. Find frequency of the letter 'o'

Ex Output:
7


Ex Input:
Sentence: 'two zebras feed on a plant through some wire mesh'. Find frequency of the letter 'o'

Ex Output:
4


Ex Input:
Sentence: 'a big door way with a surf board and window over it'. Find frequency of the letter 'w'

Ex Output:

4