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

Ex Input:
Sentence: 'a young boy bouncing a tennis ball on a tennis racquet'. Find frequency of the letter 'a'

Ex Output:
5


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 big elephant gets sprayed by a woman with a hose'. Find frequency of the letter 'e'

Ex Output:

5