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

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 person holding onto a pink kite at the beach'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a brown hawk with dead prey in a grassy area'. Find frequency of the letter 'n'

Ex Output:

2