#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=50000+10;
const int maxm=50000+10;
int n,k,r;
int ma=0;
int head[maxn];
bool vis[maxn];
struct edges
{
	int f;int t; int dist; int next;
} e[maxm];
int dfs(int x)
{	
	int re=0; vis[x]=1;
	for(int i=head[x];~i;i=e[i].next)
	{
		if(!vis[e[i].t])
		{
			int tp=dfs(e[i].t)+e[i].dist;
			if(x==r) ma=max(ma,tp);
			re+=tp;
		}
	}
	return re;
}
int tot=0;
int ans=0;
void ade(int f,int t,int d)
{
	tot++;
	e[tot].f=f;
	e[tot].t=t;
	e[tot].dist=d;
	e[tot].next=head[f];
	head[f]=tot;
}
int main()
{
	freopen("trobot.in","r",stdin);
	freopen("trobot.out","w",stdout);
	scanf("%d%d%d",&n,&r,&k);
	memset(vis,0,sizeof(vis));
	memset(head,-1,sizeof(head));
	for(int i=1;i<n;i++)
	{
		int a,b,c;
		scanf("%d%d%d",&a,&b,&c);
		ade(a,b,c);
		ade(b,a,c);
		ans+=c;
	}
	if(k==1)
	{
		int all=dfs(r);
		all=all*2-ma;
		printf("%d",all);
	}
	else
	{
		printf("%d",ans);
	}
	return 0;
}