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 crowd of people on the street one of which is taking pictures with a cell phone'. How many words start with the letter 'o' in the sentence.
Example Output: 4

Example Input: Sentence: 'a sandwich vegetables and a beer sitting on a table'. How many words start with the letter 'a' in the sentence.
Example Output: 4

Example Input: Sentence: 'a red motorcycle parked in front of a restaurant'. How many words start with the letter 'p' in the sentence.
Example Output:
1