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

Ex Input:
Sentence: 'a gourmet looking hamburger with fries on a dining table with some wine'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'two metal  benches on an empty train platform'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a commuter bus in england by a clock tower building'. Find frequency of the letter 'w'

Ex Output:

1