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

Ex Input:
Sentence: 'food sitting in bowls on table with checked tablecloth'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a train sits on a railroad track as a metal awning covers it'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'a stuffed toy dog sits and looks upright'. Find frequency of the letter 'f'

Ex Output:

2