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 cows that are standing in the grass'. Find frequency of the letter 'g'

Ex Output:
3


Ex Input:
Sentence: 'a man walking a large elephant down a dirt road'. Find frequency of the letter 'g'

Ex Output:
2


Ex Input:
Sentence: 'doughnuts on trays are displayed in a case'. Find frequency of the letter 'u'

Ex Output:

2