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

Ex Input:
Sentence: 'group of cars on the road with the sun setting behind it'. Find frequency of the letter 'd'

Ex Output:
2


Ex Input:
Sentence: 'a bunch of cows that are in the field'. Find frequency of the letter 'a'

Ex Output:
3


Ex Input:
Sentence: 'a bed with a wooden head board and a lamp next to it'. Find frequency of the letter 'n'

Ex Output:

3