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

Ex Input:
Sentence: 'a small doughnut held in a persons hand'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a couple of men standing inside of a liquor store'. Find frequency of the letter 'p'

Ex Output:
1


Ex Input:
Sentence: 'a young man wrapped in a flowered blanket'. Find frequency of the letter 'n'

Ex Output:

4