gǔ / dài / biān / mín / cháng / zài / biān / jìng / hù / shì / jiāo / huàn / mǎ / pǐ / hé / liáng / shí

古代边民常在边境互市，交换马匹和粮食。

In ancient times, people living near the border often traded with each other, exchanging horses and grain.