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

Ex Input:
Sentence: 'a traffic signal by a wire filled with some birds'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'the street sign is next to a curved road'. Find frequency of the letter 's'

Ex Output:
3


Ex Input:
Sentence: 'a little giraffe standing by a tall pole and eating the bark'. Find frequency of the letter 't'

Ex Output:

6