#include <iostream>
#include <cstdio>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <utility>
#include <numeric>
#include <algorithm>
#include <functional>
#include <cctype>
#include <complex>
#include <string>
#include <sstream>
#include <cassert>
using namespace std;

//common
typedef int  i32;
typedef long long i64,ll;
#define BR "\n"

#define ALL(c) (c).begin(),(c).end()
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define EACH(it,o) for(auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l,v,r) ((l)<=(v) && (v)<(r))

typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii;
typedef long long ll; typedef vector<long long> vl; typedef pair<long long,long long> pll; typedef vector<pair<long long,long long> > vpll;
typedef vector<string> vs; typedef long double ld;

//config
#define MODE_DEBUG
//#define INF 1<<30
//#define EPS 1e-8
//const ll MOD =100000007;

//debug
#ifdef MODE_DEBUG
#define LINE()    cerr<< " (L" << __LINE__ << ")"
#define LINELN()    LINE()<<endl

#define  DUMP(x)  cerr << #x << " = " << (x) <<endl
#define DEBUG(x) DUMP(x) << " (L" << __LINE__ << ")" << " " << __FILE__<<endl
#define CHECK(exp,act)  if(exp!=act){DUMP(exp);DEBUG(act);}
#define STOP(e)  CHECK(e,true);if(!(e)) exit(1);
#else
#define DUMP(x)
#define DEBUG(x)
#define CHECK(exp,act)
#define STOP(e)
#endif

template<class T> inline string toString(const vector<T>& x) {
	stringstream ss;
	REP(i,x.size()){
		if(i!=0)ss<<" ";
		ss<< x[i];
	}
	return ss.str();
}
template<class T> inline string toString(const vector<vector<T>>& map) {
	stringstream ss;
	REP(i,map.size()){
		if(i!=0)ss<<BR;
		ss<< toString(map[i]);
	}
	return ss.str();
}
template<class K,class V>  string toString(map<K,V>& x) {
	string res;stringstream ss;
	for(auto& p:x)ss<< p.first<<":" << p.second<<" ";
	return ss.str();
}

template<typename T,typename V> inline T mod(T v,V MOD){
	return (v%MOD+MOD)%MOD;
}

namespace ShortestPath{
    const int INF=1<<30;
    struct Edge{
        int from,to,cost;
        Edge(int from,int to,int cost)
            : from(from),to(to),cost(cost) {};
    };
    ostream& operator <<(ostream& os,const Edge& e){
            os<<"("<<e.from<<"->"<<e.to<<")";
            return os;
    }
    struct Task{
        int prev,pos,cost;
        Task(int prev,int pos,int cost)
            :prev(prev),pos(pos),cost(cost){};
        bool operator>(const Task& r) const{
            return cost>r.cost;
        }
    };
    typedef vector<vector<Edge> > Graph;
    typedef  vector<vector<int> > Mat;

    // 最大も可
    // 負の閉路が判定可能
    //O(V*E)
    vector<int> bellmanFord(Graph g,int s,vector<int> prev){
        const int V=g.size();
        vector<int> d(V,INF);d[s]=0;
        fill(ALL(prev),-2);
        REP(k,V){
            REP(i,V)REP(j,g[i].size()){
                Edge e=g[i][j];
                if(d[e.to]>d[e.from]+e.cost){
                    d[e.to]=d[e.from]+e.cost;
                    prev[e.to]=e.from;
                    if(k==V-1)d[e.to]=-INF;
                }
            }
        }
        return d;
    }    

    //verified by codoforces 144D http://codeforces.com/contest/144/submission/4976825
    // // 負の辺がない
    // // O(E*logV)
    vector<int> dijkstra(const Graph& g,const int s,vector<int>& prev){
        const int V=g.size();
        vector<int> d(V,INF);d[s]=0;
        fill(ALL(prev), -2);
        priority_queue<Task,vector<Task>,greater<Task> > que;
        que.push(Task(-1,s,0));
        while(!que.empty()){
            Task task=que.top();que.pop();
            //if(prev[task.pos]!=-2)continue;
            if(d[task.pos]<task.cost)continue;
            prev[task.pos]=task.prev;
            EACH(e,g[task.pos]){
                if(d[e->to]>d[e->from]+e->cost){
                    d[e->to]=d[e->from]+e->cost;
                    que.push(Task(e->from,e->to,d[e->to]));
                }
            }   
        }
        return d;
    }
    vector<int> dijkstra(const Graph& g,const int s){
        vector<int> prev(g.size());return dijkstra(g,s,prev);
    }

    // O(n^3) n≦100
    void warshall_floyd(Mat& d,Mat& prev){
        const int V=d.size();
        REP(k,V)
            REP(i,V)REP(j,V){
                if(d[i][j]>d[i][k] + d[k][j]){
                    d[i][j]=d[i][k] + d[k][j];
                    prev[i][j]=k;
                }
            }
    }
}
using namespace ShortestPath;

double EPS=1e-5;
int main(){
	int N,M,K;scanf("%d %d %d",&N,&M,&K);
	Graph es(N);
	REP(i,M){
		int f,t,d;scanf("%d %d %d",&f,&t,&d);f--;t--;
		es[f].push_back(Edge(f,t,d));
		es[t].push_back(Edge(t,f,d));
	}
	vector<int> ds(N,INF);
	REP(i,K){
		int l;scanf("%d",&l);l--;
		vector<int> tmp=dijkstra(es,l);

		REP(j,N)ds[j]=min(ds[j],tmp[j]);
	}
	
	double res=0;
	REP(i,N)REP(j,es[i].size()){
		double l=0,r=es[i][j].cost;
		while(r-l>EPS){
			double ml=(2*l+r)/3,mr=(l+2*r)/3;

			double lv=min(ml+ds[es[i][j].from],es[i][j].cost-ml+ds[es[i][j].to]);
			double rv=min(mr+ds[es[i][j].from],es[i][j].cost-mr+ds[es[i][j].to]);
			if(lv<=rv){
				l=ml;
			}else{
				r=mr;
			}
		}
		double v=min(l+ds[es[i][j].from],es[i][j].cost-l+ds[es[i][j].to]);
		//DUMP(l);
//		DUMP(v);
		res=max(res,v);
	}
	cout<<round(res+EPS) <<endl;
	return 0;
}

Measured memory_bytes: 5700