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

Ex Input:
Sentence: 'a surfer is in the middle of an ocean wave'. Find frequency of the letter 'i'

Ex Output:
3


Ex Input:
Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a man is swinging a bat at a ball while the catcher crouches behind him'. Find frequency of the letter 'h'

Ex Output:

6