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.*;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

public class Bb {

    private static BitSet visited;
    private static java.util.List<Integer> adjs[];
    private static java.util.List<Integer> edgeIds[];
    private static int childrenCounts[];
    private static int parents[];
    private static int parentEdges[];
    private static Deque<Integer> leaves;

    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);

        int n = in.nextInt();
        int m = in.nextInt();
        int[] ds = new int[n];
        for (int i = 0; i < n; i++) ds[i] = in.nextInt();

        adjs = new ArrayList[n];
        edgeIds = new ArrayList[n];
        for (int i = 0; i < n; i++) {
            adjs[i] = new ArrayList<>();
            edgeIds[i] = new ArrayList<>();
        }

        for (int id = 1; id <= m; id++) {
            int u = in.nextInt() - 1;
            int v = in.nextInt() - 1;
            adjs[u].add(v);
            adjs[v].add(u);
            edgeIds[u].add(id);
            edgeIds[v].add(id);
        }

        int firstMinus = -1;
        int sumParity = 0;
        for (int i = 0; i < n; i++) {
            if (ds[i] == -1 && firstMinus < 0) firstMinus = i;
            if (ds[i] == 1) sumParity += 1;
        }
        sumParity %= 2;

        if (firstMinus == -1 && sumParity == 1) {
            out.println(-1);
        } else {
            for (int i = 0; i < n; i++) {
                if (ds[i] == -1) ds[i] = i == firstMinus && sumParity == 1 ? 1 : 0;
            }

            visited = new BitSet(n);
            leaves = new ArrayDeque<>(n);
            childrenCounts = new int[n];
            parents = new int[n];
            parentEdges = new int[n];
            for (int i = 0; i < n; i++) {
                parents[i] = -1;
                parentEdges[i] = -1;
            }

            dfs(0);

            List<Integer> result = new ArrayList<>();

            while (!leaves.isEmpty()) {
                int u = leaves.removeFirst();
                int v = parents[u];
                if (v >= 0) {
                    if (ds[u] == 1) {
                        result.add(parentEdges[u]);
                        ds[v] = 1 - ds[v];
                    }
                    childrenCounts[v] -= 1;
                    if (childrenCounts[v] == 0) leaves.addLast(v);
                }
            }

            out.println(result.size());
            Collections.sort(result);
            for (int r : result) out.println(r);
        }

        out.close();
    }

    private static void dfs(int u) {
        visited.set(u);
        for (int i = 0; i < adjs[u].size(); i++) {
            int v = adjs[u].get(i);
            if (!visited.get(v)) {
                childrenCounts[u] += 1;
                parents[v] = u;
                parentEdges[v] = edgeIds[u].get(i);
                dfs(v);
            }
        }
        if (childrenCounts[u] == 0) leaves.addLast(u);
    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            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());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

    }
}
