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

Ex Input:
Sentence: 'a man riding his skateboard down low as he turns'. Find frequency of the letter 'g'

Ex Output:
1


Ex Input:
Sentence: 'a couple of men sitting next to each other under an umbrella'. Find frequency of the letter 'n'

Ex Output:
5


Ex Input:
Sentence: 'zebras and giraffes live together in their enclosure at the zoo'. Find frequency of the letter 't'

Ex Output:

5