In April this year, lots of bags full of small change  were seen at bus stops in Tianjin. They were made for passengers to turn their notes into small change. And such an idea came from four students from Zhongbei Middle School, Tianjin. "People will surely feel worried when they take a bus without coins. We just want to do something to help them," said Wang Yongcun, 15, one of the four students. The four boys spent their whole weekend making the change bags. After that they went to see the number of the passengers at each bus stop near their school, and then chose the top six stops to put the bags. Many people think that the four boys have really done a good job. But, things didn't go as the boys thought. Two days later, they found that the money was gone, and that even the bags were taken. It really made them sad but they would not give up. Their classmates and teachers came to help them in time. They put their pocket money in bags again. And the teachers also taught them to make better change bags. They tried their best to do it. The four boys feel very happy because they have done something good for the passengers. Their warm hearts are moving. More and more people are beginning to join in the activity. The change bags were put   _  .
on the buses at the bus stops under the desks near the parks