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

Ex Input:
Sentence: 'a softball player holding the bat on first base'. Find frequency of the letter 't'

Ex Output:
4


Ex Input:
Sentence: 'a white and blue plate topped with meat and a salad'. Find frequency of the letter 'u'

Ex Output:
1


Ex Input:
Sentence: 'a man flying through the air on top of a skateboard'. Find frequency of the letter 'r'

Ex Output:

3