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: 'while in a restaurant a young man is playing with his phone'. How many words start with the letter 'w' in the sentence.
Example Output: 2

Example Input: Sentence: 'several people are playing frisbee in a park'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'a man holding two ski poles and two skis'. How many words start with the letter 's' in the sentence.
Example Output:
2