When buying shoes, buy the right ones, not too small. If you are too young, you will often rub your feet. If you are too long, you will get corns.
Regular foot massage can also prevent corns.
You can use cool oil, apply cool oil to corns several times a day, and then smoke with a lit cigarette to let cool oil dissolve into corns. After a few days, the corns will fall off automatically.
Or apply potassium permanganate to corns and change potassium permanganate twice a day.
It is also a good idea to use a small amount of leek, then chop it up, break it up, and then apply it to the corns.