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: 'people seated on a table looking very happy'. Find frequency of the letter 'g'

Ex Output:
1


Ex Input:
Sentence: 'woman takes a selfie in shades while people behind her are on skis'. Find frequency of the letter 'l'

Ex Output:

3