#include<cstdio>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
#include<map>
#include<stack>
#include<iostream>
#include<list>
#include<set>
#include<cmath>
#define INF 0x7fffffff
#define eps 1e-6
#define LL long long
using namespace std;
struct lx
{
    int v,len;
};
vector<lx>g[501];
int n,m;
bool thend[501];
int d[501];
void SPFA(int start,int *dis)
{
    queue<int>q;
    bool vis[501];
    for(int i=1;i<=n;i++)
    vis[i]=0;
    dis[start]=0;
    vis[start]=1;
    q.push(start);
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int j=0; j<g[u].size(); j++)
        {
            int v=g[u][j].v;
            int len=g[u][j].len;
            if(dis[v]>dis[u]+len)
            {
                dis[v]=dis[u]+len;
                if(!vis[v])
                {
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
}

int main()
{
    while(scanf("%d%d",&m,&n)!=EOF)
    {
        for(int i=1; i<=n; i++)
            thend[i]=0,g[i].clear();
        for(int i=1; i<=m; i++)
        {
            int tmp;
            scanf("%d",&tmp);
            thend[tmp]=1;
        }
        int u,v,len;
        while(scanf("%d%d%d",&u,&v,&len)!=EOF)
        {
            lx now;
            now.len=len;
            now.v=v,g[u].push_back(now);
            now.v=u,g[v].push_back(now);
        }
        for(int i=1;i<=n;i++)
            d[i]=INF;

        for(int i=1;i<=n;i++)
            if(thend[i])
            {
                SPFA(i,d);
            }
        int minn=INF;
        int ans=1;
        for(int i=1;i<=n;i++)
        {
            int maxn=0;
            if(thend[i])continue;
            int dis[501];

            for(int j=1;j<=n;j++)
                dis[j]=d[j];
            SPFA(i,dis);

            for(int j=1;j<=n;j++)
                maxn=max(maxn,dis[j]);
            if(minn>maxn)
            {
                minn=maxn;
                ans=i;
            }
        }
        printf("%d\n",ans);
    }
}