What are the four words engraved on the stone in front of the library by Hebei Polytechnic University?

Hehe? Finally found it. It was a stone with five words "Don't forget to go back to the end of the world".

This stone is triangular, about four meters high, about one and a half meters wide at the bottom, gradually getting smaller upward, with a sharp top; The red background is engraved with the words "Tianya does not forget to return", in cursive font. The back is engraved with the word "Siyuan" in grass green. The words on this stone are probably warning students: even if you travel all over the world, you should always keep your motherland in mind and never forget your hometown and miss your alma mater; Remember to serve the motherland, go back to your hometown, repay your parents and thank your teachers.