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

Ex Input:
Sentence: 'a man in a black shirt prepares to catch a frisbee'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a pizza is in a box on a table outside'. Find frequency of the letter 'u'

Ex Output:
1


Ex Input:
Sentence: 'some people grass an orange frisbee and a building'. Find frequency of the letter 'l'

Ex Output:

2