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 long row of tables displaying lots of fruit'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a person crossing a wet street with a pretty umbrella'. Find frequency of the letter 'l'

Ex Output:

2