There was a man who had a really bad memory, so he went to the doctor to see if he could help.
The doctor told him, "I have the perfect solution! Just eat a tablespoon of vinegar every morning and your memory will improve."
The man was skeptical but decided to give it a try. He bought a bottle of vinegar and dutifully took a tablespoon every morning.
After a few weeks, he went back to the doctor and said, "Doctor, I don't think the vinegar is working. My memory is still just as bad."
The doctor thought for a moment and then asked, "What brand of vinegar are you using?"
The man replied, "I don't remember."
The doctor burst out laughing and said, "Well, it looks like the vinegar is working after all!"