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

Ex Input:
Sentence: 'a white police vehicle parked on a paved street'. Find frequency of the letter 'a'

Ex Output:
4


Ex Input:
Sentence: 'city two way street with cars lined up on both sides'. Find frequency of the letter 'h'

Ex Output:
2


Ex Input:
Sentence: 'a bearded man in a hat sitting on a bench with an obama placard'. Find frequency of the letter 'g'

Ex Output:

1