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 group of cows that are standing in the grass'. How many words start with the letter 'i' in the sentence.
Example Output: 1

Example Input: Sentence: 'a large ceramic ornament is surrounded by a flower bed and several flowers bushes and shrubs on a bright cloudy day'. How many words start with the letter 'f' in the sentence.
Example Output: 2

Example Input: Sentence: 'a man with a surfboard walking along the beach'. How many words start with the letter 'a' in the sentence.
Example Output:
3