加入
Dürer's problem: edge-unfolding convex polyhedra
Prove that every convex polyhedron can be cut along its edges and unfolded flat in one piece without overlap, or find one that cannot.
比较改动
选两个分支看看改了什么，再发起 PR 把工作带过去。
选两个不同的分支
PR 可以从任何一个分支合入任何另一个分支。