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

Ex Input:
Sentence: 'a man with a skateboard that is in the street'. Find frequency of the letter 'o'

Ex Output:
1


Ex Input:
Sentence: 'a group of cows that are standing in the grass'. Find frequency of the letter 'g'

Ex Output:
3


Ex Input:
Sentence: 'long sandwich cut into pieces set on a table next to people'. Find frequency of the letter 't'

Ex Output:

6