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

Ex Input:
Sentence: 'a man riding on the back of a white horse next to other horses'. Find frequency of the letter 'o'

Ex Output:
6


Ex Input:
Sentence: 'tow birds flying by a long necked crane'. Find frequency of the letter 'f'

Ex Output:
1


Ex Input:
Sentence: 'a pair of scissors a ruler and some pens sitting on a floor'. Find frequency of the letter 'a'

Ex Output:

5