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: 'two men on ski boards in the midst of a blizzard'. How many words start with the letter 's' in the sentence.
Example Output: 1

Example Input: Sentence: 'a picture of a zebra that is walking in the grass'. How many words start with the letter 'z' in the sentence.
Example Output: 1

Example Input: Sentence: 'multiple shots of a person doing a trick jump on a snowy hill'. How many words start with the letter 'o' in the sentence.
Example Output:
2