#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
#pragma GCC optimize 03
#pragma GCC optimize("unroll-loops")

#include <iostream>
#include <algorithm>
#include <iterator>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <vector>
#include <deque>
#include <queue>
#include <set>
#include <map>
#include <stack>
#include <string>
#include <random>
#include <numeric>
#include <unordered_set>

typedef long long ll;
typedef long double lb;

#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define file_in freopen("input.txt", "r", stdin);
#define file_in_out freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second

using namespace std;

template<typename T>
istream& operator>>(istream &in, vector<T> &v) {
    for (auto &it : v) {
        in >> it;
    }
    return in;
}

template<typename T>
ostream& operator<<(ostream &out, vector<T> &v) {
    if (!v.empty()) {
        out << v.front();
        for (int i = 1; i < v.size(); ++i) {
            out << " " << v[i];
        }
    }
    return out;
}

template<typename T>
istream& operator>>(istream &in, pair<T, T> &v) {
    in >> v.x >> v.y;
    return in;
}

template<typename T>
ostream& operator<<(ostream &out, pair<T, T> &v) {
    out << v.x << " " << v.y;
    return out;
}

const int INF = 2e9;

int s;
vector<char> spec;
vector<int> dist;
vector<vector<pair<int, int>>> g;

void bfs(int st) {
    queue<pair<int, int>> q;
    q.push({st, s});

    while (!q.empty()) {
        int v = q.front().fi;
        int now = q.front().se;
        q.pop();
        if (spec[v] == 1) {
            dist[v] = 0;
            now = s;
        }
        for (auto uu : g[v]) {
            int u = uu.fi, w = uu.se;
            if (dist[u] > dist[v] + w && now >= w) {
                dist[u] = dist[v] + w;
                q.push({u, now - w});
            }
        }
    }
}

int main() {
    fast
    // file_in
    // file_in_out

    // int start = clock();
    int n, m, k;
    cin >> n >> m >> k >> s;
    g.resize(n); spec.resize(n, 0); dist.resize(n, INF);
    int v, u, w;
    for (int i = 0; i < m; ++i) {
        cin >> v >> u >> w;
        --v; --u;
        g[v].push_back({u, w});
        g[u].push_back({v, w});
    }
    for (int i = 0; i < k; ++i) {
        cin >> v; --v;
        spec[v] = 1;
    }
    bfs(0);
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
        if (dist[i] != INF) {
            ++cnt;
        }
    }
    cout << cnt << '\n';
    for (int i = 0; i < n; ++i) {
        if (dist[i] != INF) {
            cout << i + 1 << ' ';
        }
    }
    return 0;
}