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

Ex Input:
Sentence: 'a white toilet sitting next to a bathroom sink'. Find frequency of the letter 'b'

Ex Output:
1


Ex Input:
Sentence: 'a microwave oven with a yellow note on the door'. Find frequency of the letter 'w'

Ex Output:
3


Ex Input:
Sentence: 'a panda bear is walking along the ground'. Find frequency of the letter 'g'

Ex Output:

3