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

Ex Input:
Sentence: 'two young ladies that are dancing in the room together'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'the skateboarder is jumping over a huge statue of a shoe'. Find frequency of the letter 'i'

Ex Output:
2


Ex Input:
Sentence: 'one person standing on a boat near a harbor'. Find frequency of the letter 'n'

Ex Output:

6