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

Ex Input:
Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'some sheep are standing in a grassy field'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'outdoor art display of elephant sculptures of various colorings'. Find frequency of the letter 'f'

Ex Output:

2