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

Ex Input:
Sentence: 'a piece of bread stuffed with meat and vegetables'. Find frequency of the letter 's'

Ex Output:
2


Ex Input:
Sentence: 'a guy riding a bike close to a car in the street'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'an orange and blue fire hydrant sitting on a sidewalk'. Find frequency of the letter 'i'

Ex Output:

4