In this task, you need to count the number of words in a sentence that start with the given letter. Answer with numbers and not words.

Example Input: Sentence: 'a man without a shirt riding a skateboard'. How many words start with the letter 'r' in the sentence.
Example Output: 1

Example Input: Sentence: 'a cat lying on a desk with computers'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'narrow street full of people walking during daytime'. How many words start with the letter 'd' in the sentence.
Example Output:
2