A woman entered a jewelry store, chose a ring worth a thousand reais, paid and left.
He disappeared into the store the next day and asked if he could trade it for another. This time he chose one worth two thousand reais, thanked the jeweler kindly, and prepared to leave.
The jeweler, of course, demanded another thousand reais. Outraged, the young woman said that she had already paid him the day before the value of a thousand reais and had just handed him a ring worth a thousand reais. Therefore, he owed him nothing. He then left the shop, leaving the jeweler disoriented.