3 2
1 0 1
1 2
2 3
 10 10
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
6 7
8 3
6 4
4 2
9 2
5 10
9 8
10 7
5 1
6 2

2
1
2
 0

import java.io.IOException;
import java.io.InputStream;
import java.util.*;
/*
3 3
0 0 1
1 2
2 3
1 3

 */
public class B {
	
	static InputStream is;

	public static void main(String[] args) throws IOException {
		is = System.in;
		int n = ni();
		int m = ni();
		
		int[] d= na(n);
		ArrayList<edge>[] es = new ArrayList[n];
		for (int i = 0; i < es.length; i++) {
			es[i] = new ArrayList<edge>();
		}
		
		int[] deg = new int[n];
		for (int i = 0; i < m; i++) {
			int u = ni()-1;
			int v = ni()-1;
			int id = i+1;
			es[u].add(new edge(v,id));
			es[v].add(new edge(u,id));
			deg[u]++;
			deg[v]++;
		}
		
		int minusid = -1;
		boolean[] needs = new boolean[n];
		int numneed = 0;
		for (int i = 0; i < d.length; i++) {
			if(d[i] == -1) minusid = i;
			else{
				if(deg[i] % 2 != d[i]){
					needs[i] = true;
					numneed++;
				}
			}
		}
		//System.out.println(Arrays.toString(needs));
		
		if(numneed % 2 != 0 && minusid == -1){
			System.out.println(-1);
		}
		else{
			int[] P = new int[n];
			int[] Pid = new int[n];
			boolean[] been = new boolean[n];
			
			ArrayDeque<Integer> dq = new ArrayDeque<>();
			ArrayDeque<Integer> rev = new ArrayDeque<>();
			dq.add(0);
			been[0] = true;
			while(!dq.isEmpty()){
				int at = dq.poll();
				rev.push(at);
				for(edge e : es[at]){
					if(!been[e.to]){
						P[e.to] = at;
						Pid[e.to] = e.id;
						dq.add(e.to);
						been[e.to] = true;
					}
				}
			}
			
			//System.out.println(Arrays.toString(P));
			//System.out.println(Arrays.toString(Pid));
			//System.out.println(Arrays.toString(needs));
			boolean[] tog = new boolean[n];
			boolean[] etog = new boolean[m+1];
			while(!rev.isEmpty()){
				int at = rev.pop();
				if(needs[at] || (at == minusid && numneed % 2 != 0)){
					tog[at] ^= true;
				}
				//System.out.println(at + " tog at " + tog[at] + " minusid: " + minusid);
				
				etog[Pid[at]] = tog[at];
				tog[P[at]] ^= tog[at];
			}
			
			StringBuilder stb = new StringBuilder();
			int count = 0;
			for(int i =1; i < etog.length; i++){
				if(etog[i] == false){
					count++;
					stb.append(i+"\n");
				}
			}
			System.out.println(count);
			System.out.println(stb.toString().trim());
			
		}
	}
	
	static class edge{
		int to,id;

		public edge(int to, int id) {
			this.to= to;
			this.id = id;
		}
		
	}
	
	private static byte[] inbuf = new byte[1024];
	public static int lenbuf = 0, ptrbuf = 0;
	
	private static int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private static boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private static int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private static double nd() { return Double.parseDouble(ns()); }
	private static char nc() { return (char)skip(); }
	
	private static String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private static char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private static char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private static int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private static int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
}