#include <iostream>
#include <vector>
#include <utility>
#include <queue>
#include <algorithm>

#define SHOW(d) {std::cout<<#d<<"\t:"<<d<<"\n";}
#define SHOWTOWN(t) {\
    for(size_t i=0;i<t.size();++i){\
        std::cout<<i<<":\n";\
        for(size_t j=0;j<t[i].size();++j){\
            std::cout<<"\t("<<t[i][j].first<<", "<<t[i][j].second<<")\n";\
        }\
    }\
}
#define SHOWQUEUE(a) {\
    auto t = a.front();\
    std::queue<decltype(t)> tmp(a);\
    std::cout << #a << "\t:";\
    for(size_t i=0; i<a.size(); ++i){\
        std::cout << tmp.front() << " ";\
        tmp.pop();\
    }\
    std::cout << "\n";\
}

class Comp{
    private:
    int mValue;
    public:
    Comp(int v) : mValue(v){}
    bool operator()(const std::pair<int, int>& t) const{
        return mValue==t.second;
    }
};

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    
    int n, m, k;
    std::cin >> n >> m >> k;
    std::vector<std::vector<std::pair<int, int>>> town(n);
    for(int i=0; i<m; ++i){
        int a, b, c;
        std::cin >> a >> b >> c;
        town[a-1].push_back(std::make_pair(b-1, c));
        town[b-1].push_back(std::make_pair(a-1, c));
    }
    //SHOWTOWN(town);
    std::queue<int> searchQueue;
    for(int i=0; i<n; ++i){
        searchQueue.push(i);
    }
    for(int i=0; i<k; ++i){
        int d;
        std::cin >> d;
        int queueSize = searchQueue.size();
        for(int j=0; j<queueSize; ++j){
            int searchNum = searchQueue.front();
            std::vector<std::pair<int, int>> t(town[searchNum]);
            searchQueue.pop();
            auto it = std::find_if(t.begin(), t.end(), Comp(d));
            if(it!=t.end()){
                searchQueue.push(it->first);
            }
        }
        //SHOW(i);
        //SHOWQUEUE(searchQueue);
    }
    int searchQueueNum = searchQueue.size();
    std::vector<int> ans(searchQueueNum);
    for(int i=0; i<searchQueueNum; ++i){
        ans[i]=searchQueue.front();
        searchQueue.pop();
    }
    std::sort(ans.begin(), ans.end());
    std::cout << searchQueueNum << "\n";
    for(auto i : ans){
        std::cout << i+1 << " ";
    }
    std::cout << "\n";
    
    return 0;
}