A wise man

In Brazil, there is a tramp who often wanders in the market. In people's eyes, he is a real fool, and many people often like to play tricks on him. What they often do is to put a five-dollar coin and a ten-dollar coin in the palm of their hands and let him choose. He always chooses nickels. Everyone can see that he is too stupid to tell a five-dollar coin from a ten-dollar coin. He always laughs and is very happy. Therefore, every time I see him, everyone will always have fun in this way. After a while, a very kind old woman couldn't bear to ask him, "Do you really can't tell a five-dollar coin from a ten-dollar coin?" The tramp smiled and replied, "If I take a ten-dollar coin, they won't have it next time."