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

Ex Input:
Sentence: 'men are riding on motorcycles with a man riding in their carriers'. Find frequency of the letter 'r'

Ex Output:
8


Ex Input:
Sentence: 'two elephants facing each other touching trunks in an enclosure'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'two parking meters sitting on a sidewalk near a building'. Find frequency of the letter 't'

Ex Output:

4