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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.util.Map;
import java.util.Map.Entry;
import java.util.HashMap;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Hieu Le
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskD solver = new TaskD();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskD {
        private int nSelected;
        private boolean[] selected;

        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int n = in.nextInt();
            int m = in.nextInt();
            Node[] nodes = new Node[n];

            Node root = null;
            for (int i = 0; i < n; ++i) {
                nodes[i] = new Node(in.nextInt());
                if (nodes[i].target == -1) {
                    root = nodes[i];
                }
            }

            if (root == null)
                root = nodes[0];

            for (int i = 0; i < m; ++i) {
                Node u = nodes[in.nextInt() - 1];
                Node v = nodes[in.nextInt() - 1];
                u.adj.put(v, i);
                v.adj.put(u, i);
            }

            nSelected = 0;
            selected = new boolean[m];
            root.dfs();

            if (root.target != -1 && root.target != root.current) {
                out.println(-1);
                return;
            }

            out.println(nSelected);
            for (int i = 0; i < m; ++i) {
                if (selected[i])
                    out.printf("%d ", i + 1);
            }
            out.println();
        }

        private class Node {
            private int target;
            private int current;
            private Map<Node, Integer> adj;
            private boolean visited;

            private Node(int target) {
                this.target = target;
                this.current = 0;
                adj = new HashMap<>();
                visited = false;
            }

            public void dfs() {
                this.visited = true;
                for (Map.Entry<Node, Integer> entry : adj.entrySet()) {
                    Node child = entry.getKey();
                    if (!child.visited) {
                        child.dfs();
                        if (child.target != -1 && child.target != child.current) {
                            selected[entry.getValue()] = true;  // Select this edge.
                            ++nSelected;
                            this.current = (this.current + 1) % 2;
                        }
                    }
                }
            }

        }

    }

    static class InputReader {
        private BufferedReader reader;
        private StringTokenizer tokenizer;
        private static final int BUFFER_SIZE = 32768;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(
                    new InputStreamReader(stream), BUFFER_SIZE);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}

