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

Ex Input:
Sentence: 'a giraffe sticking it's tongue out near a window'. Find frequency of the letter 'a'

Ex Output:
4


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 girl that has hit the softball in the game'. Find frequency of the letter 'b'

Ex Output:

1