#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct edge { int to, cost; };

int main(){
    int N,M,K;
    vector<edge> G[105];

    cin >> N >> M >> K;
    
    int u, v, c;
    for ( int i = 0; i < M; i++ ) {
        cin >> u >> v >> c;
        G[u].push_back((edge){v,c});
        G[v].push_back((edge){u,c});
    }
    
    vector<int> prv, nxt;
    for ( int i = 1; i <= N; i++ ) prv.push_back(i);
    for ( int i = 0; i < K; i++ ) {
        cin >> c;
        
        for ( int j = 0; j < prv.size(); j++ ) {
            int u = prv[j];
            for ( int v = 0; v < G[u].size(); v++ ) {
                if( G[u][v].cost == c) {
                    nxt.push_back(G[u][v].to);
                }
            }
        }
        
        sort(nxt.begin(), nxt.end());
        nxt.erase(unique(nxt.begin(), nxt.end()), nxt.end());
        prv.swap(nxt);
        nxt.clear();
    }
    
    cout << prv.size() << endl;
    for(int j = 0; j < prv.size(); j++) {
        if(j) cout << " ";
        cout << prv[j];
    }
    cout << endl;
}