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

Ex Input:
Sentence: 'a group of tennis players on a tennis court'. Find frequency of the letter 'o'

Ex Output:
4


Ex Input:
Sentence: 'a group of people stand inside of a big room'. Find frequency of the letter 'o'

Ex Output:
6


Ex Input:
Sentence: 'an suv with a surfboard on top is parked on a side street'. Find frequency of the letter 't'

Ex Output:

4