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

Ex Input:
Sentence: 'a bird is standing on the ledge of the building'. Find frequency of the letter 't'

Ex Output:
3


Ex Input:
Sentence: 'a small white dog looking out a car window'. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'the skateboarder is putting on a show using the picnic table as his stage'. Find frequency of the letter 't'

Ex Output:

7