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

Ex Input:
Sentence: 'flower in a vase full of water sitting on a stand '. Find frequency of the letter 'l'

Ex Output:
3


Ex Input:
Sentence: 'a plane with stairs next to it sitting in a large lot'. Find frequency of the letter 'i'

Ex Output:
6


Ex Input:
Sentence: 'a stop sign with street signs on top next to a building'. Find frequency of the letter 'e'

Ex Output:

3