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

Ex Input:
Sentence: 'a variety of a different type of vegetables'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'a black animal in dirt area below trees and rocks'. Find frequency of the letter 'n'

Ex Output:
3


Ex Input:
Sentence: 'a large brown dog sitting behind a tiger cat'. Find frequency of the letter 'b'

Ex Output:

2