// 运行超时？
//

#include "stdafx.h"
#include<iostream>
#include<map>
#include<string>
#include<vector>
#include<algorithm>


using namespace std;


int main()
{
    unsigned n;
    cin >> n;

    map<string, string> data_couple;
    for (unsigned i = 0; i < n; ++i)
    {
        string t1, t2;
        cin >> t1 >> t2;
        data_couple[t1] = t2;
        data_couple[t2] = t1;
    }

    unsigned m;
    cin >> m;

    vector<string> data_attend;
    for (unsigned i = 0; i < m; ++i)
    {
        string tmp;
        cin >> tmp;
        data_attend.push_back(tmp);
    }

    vector<string> data_sigle;
    for (auto &r : data_attend)
    {
        if (data_couple.find(r) == data_couple.end())
            data_sigle.push_back(r);
        else
        {
            auto tmp = data_couple[r];
            if (find(data_attend.begin(), data_attend.end(), tmp) == data_attend.end())
                data_sigle.push_back(r);
        }
    }

    sort(data_sigle.begin(), data_sigle.end());
    cout << data_sigle.size() << endl;
    for (size_t i = 0; i < data_sigle.size(); i++)
    {
        cout << data_sigle[i];
        if (i != (data_sigle.size() - 1))
            cout << " ";
    }

    system("pause");
    return 0;
}

```