单源最短路 

#include <iostream>
#include <cstdio>
#include <queue>
using namespace std;
int read()
{
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9')
	{
		if(c=='-')  f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9')
	{
		x=x*10+c-'0';
		c=getchar();
	}
	return f*x;
}
const int N=1e5+5;
int n,a1,b1,c1,dis[N],sum,mx;
int had[N],to[N*2],len[N*2],nxt[N*2],p;
bool f[N];
priority_queue < pair<int,int> > que;
void add(int x,int y,int z)
{
	nxt[++p]=had[x];
	to[p]=y;
	len[p]=z;
	had[x]=p;
}
int main()
{
	freopen("tour.in","r",stdin);
	freopen("tour.out","w",stdout); 
	n=read();
	for(int i=1;i<n;i++)
	{
		a1=read();  b1=read();  c1=read();
		add(a1,b1,c1);  add(b1,a1,c1);
		sum+=c1;
	}
	sum*=2;
	for(int i=2;i<=n;i++)  dis[i]=2147483647;
	que.push(make_pair(0,1));
	while(que.size())
	{
		int u=que.top().second;  que.pop();
		if(f[u])  continue;
		f[u]=1;
		for(int i=had[u];i;i=nxt[i])
		{
			int v=to[i];
			if(dis[v]>dis[u]+len[i])
			{
				dis[v]=dis[u]+len[i];
				que.push(make_pair(-dis[v],v));
			}
		}
	}
	for(int i=1;i<=n;i++)  mx=max(mx,dis[i]);
	cout<<sum-mx;
	fclose(stdin);  fclose(stdout);
	return 0;
}