#include <iostream>

 #include <cstdio>

 #include <cstring>

 #include <algorithm>

 using namespace std;

 const int inf=;

 const int MAXN=;

 int maze[MAXN][MAXN];

 bool house[MAXN];

 int dis[MAXN],fire,n;

 int main(){

     int u,v,w;

     while(scanf("%d%d",&fire,&n)!=EOF){

         memset(house,false,sizeof(house));

         for(int i=;i<MAXN;i++){

             maze[i][i]=; dis[i]=inf;

             for(int j=i+;j<MAXN;j++)

             maze[i][j]=maze[j][i]=inf;

         }

         int station;

         for(int i=;i<fire;i++){

             scanf("%d",&station);

             house[station]=true;

             dis[station]=;

         }

         while(~scanf("%d%d%d",&u,&v,&w)){

             maze[u][v]=maze[v][u]=min(w,maze[u][v]);

         }

         for(int k=;k<=n;k++){

             for(int i=;i<=n;i++){

                 for(int j=;j<=n;j++){

                     if(maze[i][k]+maze[k][j]<maze[i][j]){

                         maze[i][j]=maze[i][k]+maze[k][j];

                     }

                 }

             }

         }

         for(int i=;i<=n;i++){

             for(int j=;j<=n;j++){

                 if(house[j])

                 dis[i]=min(dis[i],maze[i][j]);

             }

         }

     //    for(int i=1;i<=n;i++)

     //    cout<<dis[i]<<endl;

         int tmp,ans,s=inf;

         for(int i=;i<=n;i++){

             tmp=;

             for(int j=;j<=n;j++){

                 tmp=max(min(dis[j],maze[i][j]),tmp);

             }

             if(tmp<s){

                 s=tmp; ans=i;

             }

         }

         printf("%d\n",ans);

     }

     return ;

 }