#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
vector<string> friends,result;
vector< pair<string,string> > pairs;
bool visited[16];
int n,m;
void clearVisited()
{
    for(int i = 0 ; i < n ; i++)
        visited[i] = false;
}
bool check()
{
    for(int i = 0 ; i < m ; i++)
    {
        bool cond1 = find(result.begin(),result.end(),pairs[i].first) != result.end();
        bool cond2 = find(result.begin(),result.end(),pairs[i].second) != result.end();
        if(cond1 && cond2)
            return false;
    }
    return true;
}
void solve(int k,int len)
{
    if(k == len+1)
    {
        if(check())
        {
            cout << len << endl;
            for(int j = 0 ; j < len ;j++)
                cout << result[j] << endl;
            exit(0);
        }
        return;
    }
    for(int i = k ; i <= n ; i++)
    {
        if(!visited[i-1])
        {
            result.push_back(friends[i-1]);
            visited[i-1] = true;
            solve(k+1,len);
            result.pop_back();
            for(int j = i ; j < n ; j++)
                visited[j] = false;
        }
    }
}
int main()
{
    string temp1,temp2;
    cin >> n >> m;
    for(int i = 0 ; i < n ; i++)
    {
        cin >> temp1;
        friends.push_back(temp1);
    }
    sort(friends.begin(),friends.end());
    for(int i = 0 ; i < m ; i++)
    {
        cin >> temp1 >> temp2;
        pairs.push_back({temp1,temp2});
    }
    for(int counter = n; counter > 0 ; counter--)
    {
        solve(1,counter);
        clearVisited();
    }
}