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

Ex Input:
Sentence: 'a double parking meter is decorated with a picture of a girl with wings on her feet'. Find frequency of the letter 'r'

Ex Output:
6


Ex Input:
Sentence: 'a tennis player after hitting a shot back to the other side of the court'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'there are plenty of sheep walking together outside the ranch'. Find frequency of the letter 'w'

Ex Output:

1