#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,M,K; cin >> N >> M >> K;
    vector<vector<pair<int,int>>> G(N);
    rep(_,M) {
        int a,b,c; cin >> a >> b >> c; a--; b--;
        G[a].push_back({b, c});
        G[b].push_back({a, c});
    }

    vector<int> can(N, 1);
    rep(_,K) {
        int d; cin >> d;
        vector<int> nt(N, 0);
        for(int i = 0; i < N; i++) if(can[i])
            for(auto [to, cost] : G[i]) if(cost == d) nt[to] = 1;
        swap(can, nt);
    }

    cout << accumulate(can.begin(), can.end(), 0) << endl;
    rep(i,N) if(can[i]) cout << i + 1 << " ";
}