include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
//-----------1065------------
const int maxn = 100010;
int couple[maxn];
int main(){
for (int i = 0; i < maxn; i++){
couple[i] = -1;
}
int n;
scanf("%d", &n);
int a, b;
while (n--){
scanf("%d %d", &a, &b);
couple[a] = b;
couple[b] = a;
}
int m;
scanf("%d", &m);
int party[10010] = {};
for (int i = 0; i < m; i++){
scanf("%d", party + i);
}
sort(party, party + m);
vector<int> ans;
for (int i = 0; i < m; i++){
int t = couple[party[i]];
if (t == -1 || !binary_search(party, party + m, t)){
ans.push_back(party[i]);
}
}
int s = ans.size();
printf("%d\n", s);
s--;
for (int i = 0; i <= s; i++){
printf("%d", ans[i]);
if (i != s)
putchar(' ');
}
return 0;
}