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

Ex Input:
Sentence: 'a police officer who is riding on a horse'. Find frequency of the letter 'p'

Ex Output:
1


Ex Input:
Sentence: 'baseball player reaching back as he's about to throw the ball'. Find frequency of the letter 'e'

Ex Output:
5


Ex Input:
Sentence: 'a young lady is attempting to control the soccer ball as another looks on'. Find frequency of the letter 't'

Ex Output:

7