#include <bits/stdc++.h>
//#include<boost/multiprecision/cpp_int.hpp>
//#include<boost/multiprecision/cpp_dec_float.hpp>
//#include <atcoder/all>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll INF = 1LL << 60;

// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

//using lll=boost::multiprecision::cpp_int;
//using Double=boost::multiprecision::number<boost::multiprecision::cpp_dec_float<1024>>;//仮数部が1024桁
template <class T>
inline bool chmin(T &a, T b)
{
	if (a > b)
	{
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
	if (a < b)
	{
		a = b;
		return true;
	}
	return false;
}

template <typename T>
T mypow(T x, T n, const T &p = -1)
{ //x^nをmodで割った余り

	if(p!=-1){
		x%=p;
	}
	T ret = 1;
	while (n > 0)
	{
		if (n & 1)
		{
			if (p != -1)
				ret = (ret * x) % p;
			else
				ret *= x;
		}
		if (p != -1)
			x = (x * x) % p;
		else
			x *= x;
		n >>= 1;
	}
	return ret;
}

using namespace std;
//using namespace atcoder;

struct edge{
	int to,cost;
	edge(int a,int b):to(a),cost(b){}
};

bool dp[1005][105];
void solve()
{	
	int n,m,k;
	cin>>n>>m>>k;
	vector<vector<edge>>g(n);
	rep(i,m){
		int a,b,c;
		cin>>a>>b>>c;
		a--;b--;
		g[a].eb(b,c);
		g[b].eb(a,c);
	}
	vector<int>d(k);
	rep(i,k)cin>>d[i];
	reverse(all(d));
	vector<int>ans;
	rep(i,n){
		memset(dp,false,sizeof(dp));
		dp[0][i]=true;
		rep(j,k){
			rep(x,n){
				for(auto e:g[x]){
					if(d[j]==e.cost)dp[j+1][e.to]|=dp[j][x];
				}
			}
		}
		rep(j,n){
			if(dp[k][j]){
				ans.eb(i+1);
				break;
			}
		}
	}
	cout<<ans.size()<<"\n";
	rep(i,ans.size()){
		cout<<ans[i]<<(i==ans.size()-1?"\n":" ");
	}
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}