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

Ex Input:
Sentence: 'a girl that has a kite in the air'. Find frequency of the letter 'r'

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: 'a man with a large grey and black beard and glasses and a tie'. Find frequency of the letter 'e'

Ex Output:

5