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

Ex Input:
Sentence: 'there is a person standing on a blue towel'. Find frequency of the letter 'n'

Ex Output:
4


Ex Input:
Sentence: 'a knife a cutting board some bananas and a toaster'. Find frequency of the letter 'i'

Ex Output:
2


Ex Input:
Sentence: 'a boat carries a smaller motorboat that is hitched on the back'. Find frequency of the letter 'c'

Ex Output:

3