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

Ex Input:
Sentence: 'a blue fire hydrant painted on the bottom of it'. Find frequency of the letter 'h'

Ex Output:
2


Ex Input:
Sentence: 'a person is holding a chocolate doughnut with rainbow sprinkles'. Find frequency of the letter 's'

Ex Output:
4


Ex Input:
Sentence: 'a cat is laying in a bowl with a receipt'. Find frequency of the letter 'o'

Ex Output:

1