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

Ex Input:
Sentence: 'a mixed bouquet of flowers in a glass vase set before a window'. Find frequency of the letter 'w'

Ex Output:
3


Ex Input:
Sentence: 'a woman cross country skiing in a competition'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'someone is trying to pull of a skateboard trick'. Find frequency of the letter 'l'

Ex Output:

2