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

Ex Input:
Sentence: 'an elephant with broken tusks stands in front of a hill and boulders'. Find frequency of the letter 'n'

Ex Output:
7


Ex Input:
Sentence: 'an old woman is holding her cat in front of a camera'. Find frequency of the letter 'r'

Ex Output:
3


Ex Input:
Sentence: 'pair of cats expressing the same confused face'. Find frequency of the letter 's'

Ex Output:

5