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: 'three young people goofing around; one of the guys has a football, the girl has a teddy bear'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a herd of zebra standing next to each other near a rocky hillside'. Find frequency of the letter 'i'

Ex Output:

3