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

Ex Input:
Sentence: 'a herd of horses standing next to each other on a field'. Find frequency of the letter 'r'

Ex Output:
3


Ex Input:
Sentence: 'the counter of a doctor's office, including a laptop, cotton swabs, and tongue depressors'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'a cat standing on steps who is tied outside on a leash'. Find frequency of the letter 'c'

Ex Output:

1