package yukicoder;

import java.util.Scanner;
import java.util.List;
import java.util.ArrayList;

public class No1477 {
	
	private static class Peek {
		public int i, A;
		public List<Integer> V;
		public boolean B;
		public Peek(int i, int A) {
			this.i = i;
			this.A = A;
			V = new ArrayList<Integer>();
			B = false;
		}
	}

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int M = scan.nextInt();
		Peek[] A = new Peek[N];
		for (int i=0; i < N; i++) {
			A[i] = new Peek(i, scan.nextInt());
		}
		for (int i = 0; i < M; i++) {
			int u = scan.nextInt() - 1;
			int v = scan.nextInt() - 1;
			A[u].V.add(v);
			A[v].V.add(u);
		}
		int K = scan.nextInt();
		for (int i = 0; i < K; i++) {
			int b = scan.nextInt() - 1;
			A[b].B = true;
		}
		scan.close();
		List<Peek> S = new ArrayList<Peek>();
		for (Peek p : A) {
			boolean noInput = true;
			List<Integer> rlist = new ArrayList<Integer>();
			for (int i : p.V) {
				if (p.A > A[i].A) {
					noInput = false;
				} else if (p.A == A[i].A) {
					rlist.add(i);
				}
			}
			for (int i : rlist) {
				p.V.remove((Object)i);
			}
			if (noInput) {
				S.add(p);
			}
		}
		List<Integer> op = new ArrayList<Integer>();
		while(!S.isEmpty()) {
			Peek n = S.remove(0);
			boolean b = n.B;
			if (b) {
				n.B = false;
				op.add(n.i + 1);
			}
			for (int i : n.V) {
				Peek m = A[i];
				m.V.remove((Object)n.i);
				if (b) {
					m.B = !m.B;
				}
				boolean noInput = true;
				List<Integer> rlist = new ArrayList<Integer>();
				for (int j : m.V) {
					if (m.A > A[j].A) {
						noInput = false;
					} else if (m.A == A[j].A) {
						rlist.add(j);
					}
				}
				for (int j : rlist) {
					m.V.remove((Object)j);
				}
				if (noInput) {
					S.add(m);
				}
			}
		}
		boolean b = false;
		for (Peek p : A) {
			b |= p.B;
		}
		if (b) {
			System.out.println(-1);
		} else {
			System.out.println(op.size());
			for (int p : op) {
				System.out.println(p);
			}
		}
	}

}