#include<bits/stdc++.h>
using namespace std;
vector<pair<int,int>>adj[100005];
pair<int,int> dis[100005][2];
vector<int>sp;
struct state{
int root,dis,cur;
state(int r,int d,int c){
root=r,dis=d,cur=c;
}
friend bool operator<(state a,state b){
return a.dis>b.dis;
}
};
int inf=1e9;
priority_queue<state>pq;
int can(pair<int,pair<int,int>>ans1,pair<int,pair<int,int>>ans2){
if(ans1.first==inf||ans2.first==inf)return inf;
bool temp=(ans1.second.first!=ans2.second.first&&ans1.second.first!=ans2.second.second&&ans1.second.second!=ans2.second.first&&ans1.second.second!=ans2.second.second);
if(temp)return ans1.first+ans2.first;
else return inf;
}
map<pair<int,int>,int>mp;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n,m,k;cin>>n>>m>>k;
for(int i=0;i<m;i++){
int u,v,w;cin>>u>>v>>w;
adj[u].push_back({v,w});
adj[v].push_back({u,w});
}
for(int i=1;i<=k;i++){
int x;cin>>x;
sp.push_back(x);
pq.push(state(x,0,x));
dis[x][0]={0,x};
}
for(int i=0;i<=n;i++)dis[i][0]=dis[i][1]={inf,inf};
while(!pq.empty()){
int d=pq.top().dis;
int x=pq.top().cur;
int r=pq.top().root;
pq.pop();
if(d<dis[x][0].first)dis[x][1]=dis[x][0],dis[x][0]={d,r};
else if(d<dis[x][1].first&&r!=dis[x][0].second)dis[x][1]={d,r};
else continue;
for(auto v:adj[x]){
pq.push({state(r,d+v.second,v.first)});
}
}
int rans=inf;
pair<int,pair<int,int>>ans[4];
for(int i=0;i<4;i++){
ans[i]={inf,{inf,inf}};
}
for(int i=1;i<=n;i++){
int val=dis[i][0].first+dis[i][1].first;
int x=dis[i][0].second;
int y=dis[i][1].second;
if(x>y)swap(x,y);
if(mp[{x,y}]==0||mp[{x,y}]>val)mp[{x,y}]=val;
}
for(auto x:mp){
int val=x.second;
int u=x.first.first;
int v=x.first.second;
if(val<ans[0].first){
ans[3]=ans[2];
ans[2]=ans[1];
ans[1]=ans[0];
ans[0]={val,{u,v}};
}else if(val<ans[1].first){
ans[3]=ans[2];
ans[2]=ans[1];
ans[1]={val,{u,v}};
}else if(val<ans[2].first){
ans[3]=ans[2];
ans[2]={val,{u,v}};
}else if(val<ans[3].first){
ans[3]={val,{u,v}};
}
}
for(int i=0;i<3;i++){
for(int j=i+1;j<3;j++){
rans=min(rans,can(ans[i],ans[j]));
}
}
cout<<(rans==inf?-1:rans);
}
