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

Ex Input:
Sentence: 'a group of people standing around a table filled with assorted electronic devices'. Find frequency of the letter 'w'

Ex Output:
1


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

Ex Output:
4


Ex Input:
Sentence: 'a black cat sitting in a black suitcase'. Find frequency of the letter 'b'

Ex Output:

2