#include <iostream>
#include <string>
#include <map>
#include <utility>
#include <cstdlib>
#include <vector>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#define ll long long

using namespace std;

struct e{
    int to,cost;
};

vector<vector<e> >es;
vector<int> costs;
vector<int> ans;

int used[101][1001];
int ek;
void dfs(int v,int k){
    if(used[v][k] == 1)return;
    used[v][k] = 1;
    if(k == ek){
        ans.push_back(v);
        return;
    }
    for(int i=0;i<es[v].size();i++){
        if(es[v][i].cost == costs[k])dfs(es[v][i].to,k+1);
    }
}

int main(void){
	int n,m;
    cin >> n >> m >> ek;
    es.resize(n);costs.resize(ek);
    for(int i=0;i<m;i++){
        int a,b,c;
        cin >> a >> b >> c;
        a--;b--;
        es[a].push_back(e{b,c});
        es[b].push_back(e{a,c});
    }
    for(int i=0;i<ek;i++){
        cin >> costs[i];
    }

    for(int i=0;i<n;i++){
        memset(used,0,sizeof(0));
        dfs(i,0);
    }
    vector<int> ret;
    int pre = -1;
    for(int i=0;i<ans.size();i++){
        if(pre != ans[i]){
            ret.push_back(ans[i]);
            pre = ans[i];
        }
    }

    sort(begin(ret),end(ret));
    cout << ret.size() << endl;
    for(int i=0;i<ret.size();i++){
        cout << ret[i]+1;
        if(i!=ret.size()-1)cout << " ";
        else cout << endl;
    }

    return 0;
}