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

Ex Input:
Sentence: 'a line of people on motorcycles on the road'. Find frequency of the letter 'e'

Ex Output:
5


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 number of fruits on display at a market'. Find frequency of the letter 'k'

Ex Output:

1