在遇到这种转移：
fu,0=∑v∈sonufv,1f_{u,0}=\sum_{v\in son_u} f_{v,1}fu,0=∑v∈sonufv,1
fu,1=au+∑v∈sonumin(fv,0,fv,1)f_{u,1}=a_u+\sum_{v\in son_u}\min(f_{v,0},f_{v,1})fu,1=au+∑v∈sonumin(fv,0,fv,1)
第二种的 min(fv,0,fv,1)\min(f_{v,0},f_{v,1})min(fv,0,fv,1) 在线段树合并时怎么转移啊
