22-year-old Zhang Heng decided to celebrate his college graduation with a 20-day bicycle trip across China with six of his friends.

90 miles into their trip, in Yajiang, Zhang found a stray dog in the street. Zhang fed it, and the dog ran after them.

And he CONTINUED to follow them for the rest of their 20-day trip...which was more than 1,100 miles. (Yajiang is in the center of the country, 1,400 miles southwest of Beijing.)

They eventually named the dog Xiao Sa. (It's pronounced she-ow sah.) It even climbed mountains that were over 13,000 feet tall as the group made their way to Tibet.

The only time Xiao Sa didn't run was on one super-steep downhill slope. The bikes went as fast as 40 miles an hour, so Zhang mounted a cage on his bike so the dog wouldn't have to run to keep up.

And Zhang adopted Xiao Sa after the trip was over.