If you can't find the keyboard given by the software, you can enter "Yes" in the input method, and there will be a symbol √.

Excellent Mathematics is an online mathematics learning product for junior and senior high school students! It can synchronize classroom teaching, complete homework assigned by teachers online, practice math problems independently, and see your real learning situation through big data statistics, which really helps you improve your math scores.

Just enter the pinyin "dui" on the phone keyboard and it will come out.