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

Ex Input:
Sentence: 'a man hitting a tennis ball with a tennis racquet'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a group of men standing on the side of a boat'. Find frequency of the letter 'o'

Ex Output:
5


Ex Input:
Sentence: 'a couple of bears that looks like they are hugging'. Find frequency of the letter 'u'

Ex Output:

2