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

Ex Input:
Sentence: 'salad and vegetables with me on top of plate'. Find frequency of the letter 'o'

Ex Output:
3


Ex Input:
Sentence: 'some giraffes moving across a big grass field'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a train that says "santa fe vista canyon"'. Find frequency of the letter 'y'

Ex Output:

2