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

Ex Input:
Sentence: 'a baseball player dropping his bat and starting to run'. Find frequency of the letter 'o'

Ex Output:
2


Ex Input:
Sentence: 'a piece of bread stuffed with meat and vegetables'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a black and white clock on a red building'. Find frequency of the letter 'd'

Ex Output:

3