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

Ex Input:
Sentence: 'a man in a black shirt prepares to catch a frisbee'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a group of people are playing soccer on a beach'. Find frequency of the letter 'l'

Ex Output:
2


Ex Input:
Sentence: 'two planes flying side by side through a clear sky'. Find frequency of the letter 't'

Ex Output:

2