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

Ex Input:
Sentence: 'a grey hummingbird by fence and tree branches'. Find frequency of the letter 'y'

Ex Output:
2


Ex Input:
Sentence: 'a gray airplane with metal petals on the wings takes off from an airport'. Find frequency of the letter 'i'

Ex Output:
4


Ex Input:
Sentence: 'a sandwich with pickles, crackers and chili on a plate'. Find frequency of the letter 'h'

Ex Output:

3