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 a white surfboard on a large wave'. Find frequency of the letter 'a'

Ex Output:
7


Ex Input:
Sentence: 'a man pushing a cart full of bananas'. Find frequency of the letter 'u'

Ex Output:
2


Ex Input:
Sentence: 'a piece of pizza with cheese and meat with sauce and a salad'. Find frequency of the letter 'e'

Ex Output:

7