From all vertices with degree 0 (not necessarily leaves), choose two vertices with less weight and add a branch point. It takes these two vertices as children, and its weight is equal to the sum of the weights of these two children. Repeat the above operations until only 1 vertices with degree 0 remain.

A tree is a weighted node, and then multiplied by the number of layers. The general map right is written directly on the edge, which is the edge right.