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.Arrays;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import java.io.BufferedReader;
import java.util.Collections;
import java.io.InputStream;

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

    static class TaskD {
        int n;
        int m;
        int[] d;
        ArrayList<Pair>[] Edges;
        Boolean[] visited;
        List<Integer> ans;

        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            n = in.nextInt();
            m = in.nextInt();

            d = new int[n + 1];
            int cntOdd = 0, cntNeg = 0;
            for (int i = 1; i <= n; i++) {
                d[i] = in.nextInt();
                if (d[i] == -1) {
                    cntNeg++;
                } else if (d[i] == 1) {
                    cntOdd++;
                }
            }

            if (cntOdd % 2 == 1 && cntNeg == 0) {
                out.print("-1");
                return;
            }

            int fl = 0;
            if (cntOdd % 2 == 1) fl = 1;
            for (int i = 1; i <= n; i++) {
                if (d[i] == -1) {
                    d[i] = fl;
                    fl = 0;
                }
            }
            Edges = new ArrayList[n + 1];
            for (int i = 1; i <= n; i++) {
                Edges[i] = new ArrayList<>();
            }

            for (int i = 1; i <= m; i++) {
                int x = in.nextInt();
                int y = in.nextInt();

                Edges[x].add(new Pair(y, i));
                Edges[y].add(new Pair(x, i));
            }
            visited = new Boolean[n + 1];
            Arrays.fill(visited, false);
            ans = new ArrayList<>();
            dfs(1);
            out.println(ans.size());
            Collections.sort(ans);
            ans.forEach(out::println);
        }

        private int dfs(int u) {
            visited[u] = true;
            int ret = d[u];

            for (Pair g : Edges[u]) {
                int f = g.first;
                if (visited[f]) continue;
                if (dfs(f) == 1) {
                    ret ^= 1;
                    ans.add(g.second);
                }
            }
            return ret;
        }

        private class Pair {
            int first;
            int second;

            public Pair(int first, int second) {
                this.first = first;
                this.second = second;
            }

        }

    }

    static class FastScanner {
        private BufferedReader bufferedReader;
        private StringTokenizer stringTokenizer;

        public FastScanner(InputStream inputStream) {
            bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        }

        public String next() {
            if (stringTokenizer == null || !stringTokenizer.hasMoreElements()) {
                try {
                    stringTokenizer = new StringTokenizer(bufferedReader.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return stringTokenizer.nextToken();
        }

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

    }
}

