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

Ex Input:
Sentence: 'a man standing on a tennis court holding a racquet'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a woman holds some baked goods at the convention'. Find frequency of the letter 'd'

Ex Output:
3


Ex Input:
Sentence: 'a lady is standing near a luggage stand at the air port'. Find frequency of the letter 'a'

Ex Output:

9