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

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 man flying through the air on top of a skateboard'. Find frequency of the letter 'h'

Ex Output:
3


Ex Input:
Sentence: 'a beautiful young woman serving a tennis ball on a tennis court'. Find frequency of the letter 'i'

Ex Output:

4