#include<iostream>
#include<math.h>
#include<vector>
#include <array>
#include <algorithm>
#include <queue>
#include <numeric>
#include <map>

using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) //printf(__VA_ARGS__)

typedef pair<int, int> pos;
int pos::*x = &pos::first;
int pos::*y = &pos::second;

int dxy[] = {0, 1, 0, -1, 0};

/*================================*/

/*
N M K
a1 b1 c1
⋮
aM bM cM
d1 … dK
*/

vector<int> roads[100][100];
int N, M, K;
vector<int> costs(1000);

bool search(int n, int d) {
    if (d == K) return true;
    REP(i,N) {
        REP(j,roads[n][i].size()) {
            if (roads[n][i][j] == costs[K - d - 1]) {
                if (search(i, d+1)) return true;
            }
        }
    }
    return false;
}

signed main()
{
    cin >> N >> M >> K;
    int a, b, c;
    REP(i,M) {
        cin >> a >> b >> c;
        roads[a-1][b-1].push_back(c);
        roads[b-1][a-1].push_back(c);
    };

    REP(k,K) cin >> costs[k];

    vector<int> ok(N);
    int cnt = 0;
    REP(i,N) {
        ok[i] = search(i, 0);
        cnt += ok[i];
    }
    cout << cnt << endl;
    a = 0;
    REP(i,N) {
        if (ok[i]) {
            if (a == 0) a++;
            else cout << " ";
            cout << i + 1;
        }
    }
    cout << endl;

    return 0;
}