"I used to think security checking was an easy job, but I learned that many things were not as easy as I imagined. The requirement was strict, and we had to master enough knowledge of the procedures to be able to work," says Chen.

In the truck-checking area, Gao worked in a team with three of his schoolmates. "One of us led the truck driver to a security check, another checked the outside of the truck, including the roof and the underside, and the other two checked the cabin for any prohibited objects," says Gao.

"Although the work seemed to be repetitive, it was interesting. For example, some drivers wanted to smoke, so they would hide their lighters, and we had to find them," he adds.

Each of them had to work eight hours a day, but they didn't feel tired.

"They cherished the opportunity very much, so they worked hard and actively, dedicating themselves to completing their tasks," says Li.

He was responsible for taking care of the students during this period. Before the journey, he worried whether the students would get accustomed to life in Beijing, if they would feel tired of their work, or if they would get ill.

So he accompanied the students, helped them work and cared about their feelings. It turns out the students did a good job there without feeling uncomfortable.