神**所有点都爆int，我还以为我写出什么大锅了，不开long long见祖宗。。。
动态点分治利用点分树树高不超过log的性质，我们对每个点维护一个子树和，一个点分树子树和，一个点分树上父亲的子树和。修改直接爬点分树，查询在点分树上往答案较小的儿子上跳，如果儿子都不如自己优说明自己就是最优的
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=,inf=1e9;
int n,c,T,t1,t2,t3,cnt,Cnt,sizz;
int p[N],noww[*N],goal[*N],val[*N];
int siz[N],dep[N],far[N],imp[N],top[N],dis[N];
int P[N],Noww[*N],Goal[*N],Val[*N];
int sze[N],maxx[N],vis[N],fer[N];
long long sum[N],dst[N][];
void Link(int f,int t,int v)
{
noww[++cnt]=p[f],p[f]=cnt;
goal[cnt]=t,val[cnt]=v;
noww[++cnt]=p[t],p[t]=cnt;
goal[cnt]=f,val[cnt]=v;
}
void Linka(int f,int t,int v)
{
Noww[++Cnt]=P[f],P[f]=Cnt;
Goal[Cnt]=t,Val[Cnt]=v;
Noww[++Cnt]=P[t],P[t]=Cnt;
Goal[Cnt]=f,Val[Cnt]=v;
}
void DFS(int nde,int fth,int dth)
{
int tmp=;
siz[nde]=,far[nde]=fth,dep[nde]=dth;
for(int i=p[nde];i;i=noww[i])
if(goal[i]!=fth)
{
dis[goal[i]]=dis[nde]+val[i];
DFS(goal[i],nde,dth+);
siz[nde]+=siz[goal[i]];
if(siz[goal[i]]>tmp)
tmp=siz[goal[i]],imp[nde]=goal[i];
}
}
void Gettop(int nde,int tpp)
{
top[nde]=tpp;
if(imp[nde])
{
Gettop(imp[nde],tpp);
for(int i=p[nde];i;i=noww[i])
if(goal[i]!=far[nde]&&goal[i]!=imp[nde])
Gettop(goal[i],goal[i]);
}
}
int LCA(int x,int y)
{
while(top[x]!=top[y])
{
if(dep[top[x]]<dep[top[y]])
swap(x,y); x=far[top[x]];
}
return dep[x]<dep[y]?x:y;
}
long long Dist(int x,int y)
{
int lca=LCA(x,y);
return dis[x]+dis[y]-*dis[lca];
}
void Mark(int nde,int fth)
{
sze[nde]=,maxx[nde]=;
for(int i=p[nde];i;i=noww[i])
if(goal[i]!=fth&&!vis[goal[i]])
{
Mark(goal[i],nde);
sze[nde]+=sze[goal[i]];
maxx[nde]=max(maxx[nde],sze[goal[i]]);
}
maxx[nde]=max(maxx[nde],sizz-sze[nde]);
if(maxx[nde]<maxx[c]) c=nde;
}
void Create(int nde,int fth)
{
vis[nde]=true,fer[nde]=fth;
for(int i=p[nde];i;i=noww[i])
if(!vis[goal[i]])
{
sizz=sze[goal[i]],maxx[c=]=sze[goal[i]];
Mark(goal[i],),Linka(nde,c,goal[i]),Create(c,nde);
}
}
void Change(int nde,int tsk)
{
sum[nde]+=tsk; int mem=nde;
while(fer[nde])
{
long long dist=Dist(fer[nde],mem)*tsk;
dst[fer[nde]][]+=dist,dst[nde][]+=dist;
sum[fer[nde]]+=tsk,nde=fer[nde];
}
}
long long Getans(int nde)
{
long long ret=dst[nde][]; int mem=nde;
while(fer[nde])
{
long long dist=Dist(fer[nde],mem);
ret+=dst[fer[nde]][]-dst[nde][];
ret+=dist*(sum[fer[nde]]-sum[nde]);
nde=fer[nde];
}
return ret;
}
long long Query(int nde)
{
long long ret=Getans(nde);
for(int i=P[nde];i;i=Noww[i])
if(Getans(Val[i])<ret)
return Query(Goal[i]);
return ret;
}
int main()
{
scanf("%d%d",&n,&T);
for(int i=;i<n;i++)
scanf("%d%d%d",&t1,&t2,&t3),Link(t1,t2,t3);
DFS(,,),Gettop(,);
sizz=n,maxx[c=]=n,Mark(,);
int mem=c; Create(c,),c=mem;
while(T--)
{
scanf("%d%d",&t1,&t2);
Change(t1,t2),printf("%lld\n",Query(c));
}
return ;
}