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

Ex Input:
Sentence: 'a cooked pizza on a silver platter with another in the background'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a man riding a skateboard up the side of a ramp'. Find frequency of the letter 'u'

Ex Output:
1


Ex Input:
Sentence: 'an breakfast sandwich and a coffee on a table'. Find frequency of the letter 'k'

Ex Output:

1