#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <algorithm>
#include <sstream>
#include <map>
#include <set>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<30
#define pb push_back
#define mp make_pair

using namespace std;
typedef long long ll;
typedef pair<int,int> P;

struct edge {
    int from,to;
    int cost;

    edge(int t,int c) : to(t),cost(c) {}
    edge(int f,int t,int c) : from(f),to(t),cost(c) {}

    bool operator<(const edge &e) const {
        return cost < e.cost;
    }
};

vector<edge> G[105];
vector<int> v,ans;
int n,m,k;

void dfs(int now,int j) {
    if(j == k) {
        ans.push_back(now);
        return;
    }

    rep(i,G[now].size()) {
        edge e = G[now][i];
        if(e.cost == v[j]) {
            dfs(e.to,j+1);
        }
    }
}

int main() {
    cin >> n >> m >> k;

    rep(i,m) {
        int a,b,c;
        cin >> a >> b >> c;

        a--;
        b--;

        G[a].push_back(edge(b,c));
        G[b].push_back(edge(a,c));
    }

    v.resize(k);
    rep(i,k) cin >> v[i];

    rep(i,n) {
        dfs(i,0);
    }

    ans.erase(unique(ans.begin(),ans.end()),ans.end());
    sort(ans.begin(),ans.end());

    cout << ans.size() << endl;
    rep(i,ans.size()) {
        cout << ans[i]+1;

        if(i == ans.size()-1) cout << endl;
        else cout << " ";
    }

    return 0;
}