#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn=105000;
int d[maxn], fa[maxn];
struct Edge{int u,v,dis;};
vector<int> G[maxn];vector<Edge> edges;
int n, ans;
int val[maxn], vis[maxn];
void Addedge(int u,int v,int dis){
    edges.push_back((Edge){u,v,dis});edges.push_back((Edge){v,u,dis});
    int m=edges.size()-1;G[u].push_back(m-1);G[v].push_back(m);
}
int dfs(int x,int f,int depth){
    fa[x]=f; d[x]=depth;
    for(int i=0;i<G[x].size();i++){
        Edge v=edges[G[x][i]];
        if(v.v==f) continue;
        dfs(v.v,x,depth+v.dis);
        if(vis[v.v]) vis[x]=1,ans+=edges[G[x][i]].dis*2;
    }
}
int main(){
    int n,k,a,b,c;
    scanf("%d%d",&n,&k);
    for(int i=0;i<n-1;i++){
        scanf("%d%d%d",&a,&b,&c);
        Addedge(a,b,c);
    }
    int m; scanf("%d",&m);
    for(int i=0;i<m;i++){
        scanf("%d",&val[i]); vis[val[i]]=1;
    }
    dfs(k,0,0);
    int maxnum=0;
    for(int i=1;i<=n;i++){
        if(vis[i]) maxnum=max(maxnum,d[i]);
    }
    printf("%d",ans- maxnum);
    return 0;
}
/*
4 2
1 2 1
4 2 2
2 3 3
1
1
*/