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

Ex Input:
Sentence: 'a little child looking up to a camera holding a cell phone'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'a close up of a train on a track in the dark'. Find frequency of the letter 'a'

Ex Output:
6


Ex Input:
Sentence: 'two giraffes standing in a dirt lot next to a building'. Find frequency of the letter 'n'

Ex Output:

5