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

Ex Input:
Sentence: 'a cooked pizza on a silver platter with another in the background'. Find frequency of the letter 'e'

Ex Output:
5


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: 'cars are parked alongside the road and a man is standing next to a sign'. Find frequency of the letter 'd'

Ex Output:

5