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

Ex Input:
Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'

Ex Output:
2


Ex Input:
Sentence: 'a woman holds a wine glass upside down while wearing rabbit ears and staring at a bottle of wine'. Find frequency of the letter 'a'

Ex Output:
11


Ex Input:
Sentence: 'a shiny silver water pipe sticking out of the sidewalk'. Find frequency of the letter 'w'

Ex Output:

2