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.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Calendar;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.SortedSet;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * #
 * @author pttrung
 */
public class B_Round_429_Div1 {

    public static long MOD = 1000000007;

    public static void main(String[] args) throws FileNotFoundException {
        // PrintWriter out = new PrintWriter(new FileOutputStream(new File(
        // "output.txt")));
        PrintWriter out = new PrintWriter(System.out);
        Scanner in = new Scanner();
        int n = in.nextInt();
        int m = in.nextInt();
        int[] data = new int[n];
        ArrayList<Integer>[] map = new ArrayList[n];

        for (int i = 0; i < n; i++) {
            map[i] = new ArrayList();
            data[i] = in.nextInt();

        }
        int[][] edge = new int[m][2];
        int[] count = new int[n];

        for (int i = 0; i < m; i++) {
            for (int j = 0; j < 2; j++) {
                edge[i][j] = in.nextInt() - 1;
                count[edge[i][j]]++;
            }
            map[edge[i][0]].add(i);
            map[edge[i][1]].add(i);

        }
        boolean[] check = new boolean[m];
        boolean[] special = new boolean[n];
        int[] pa = new int[n];
        Arrays.fill(pa, -1);
        int root = -1;
        for (int i = 0; i < n; i++) {
            if (data[i] != -1 && count[i] % 2 != data[i]) {
                root = i;
                LinkedList<Integer> q = new LinkedList();
                q.add(i);
                pa[i] = i;
                while (!q.isEmpty()) {
                    int node = q.poll();
                    for (int j : map[node]) {
                        int nxt = nxt(edge[j], node);
                        if (pa[nxt] == -1) {
                            pa[nxt] = j;
                            q.add(nxt);
                        }
                    }
                }
                break;
            }
        }
        boolean ok = false;
        int total = 0;
        int re = m;
        int other = -1;
        for (int i = 0; i < n; i++) {
            if (data[i] != -1 && count[i] % 2 != data[i]) {
                special[i] = true;
                total++;
                int st = i;
                while (st != root && !check[pa[st]]) {
                    check[pa[st]] = true;
                    st = nxt(edge[pa[st]], st);
                    if (data[st] == -1) {
                        ok = true;
                    }
                    re--;
                }
            } else if (data[i] == -1) {
                other = i;
            }
        }
        if (ok || total % 2 == 0) {
            ok = true;
        } else if (other != -1) {
            total++;
            special[other] = true;
            ok = true;
            int st = other;
            while (st != root && !check[pa[st]]) {
                check[pa[st]] = true;
                st = nxt(edge[pa[st]], st);
                re--;
            }
        }
        if (!ok) {
            out.println(-1);
        } else {
            int[] level = new int[n];
            int[] num = new int[n];
            if (root != -1) {
                for (int i = 0; i < n; i++) {
                    map[i] = new ArrayList();
                }
                for (int i = 0; i < m; i++) {
                    if (check[i]) {
                        int u = edge[i][0];
                        int v = edge[i][1];
                        map[u].add(i);
                        map[v].add(i);
                    }
                }

                update(root, root, edge, special, level, num, map);
                for (int i = 0; i < m; i++) {
                    if (check[i]) {
                        int u = edge[i][0];
                        int v = edge[i][1];
                        if (level[u] < level[v]) {
                            if (num[v] % 2 == 0) {
                                check[i] = false;
                                re++;
                            }
                        } else {
                            if (num[u] % 2 == 0) {
                                check[i] = false;
                                re++;
                            }
                        }
                    }
                }
            }

            int[] post = new int[n];
            for (int i = 0; i < m; i++) {
                if (!check[i]) {
                    post[edge[i][0]]++;
                    post[edge[i][1]]++;
                    //System.out.println(Arrays.toString(edge[i]));

                }
            }
            for (int i = 0; i < n; i++) {
                if (data[i] != -1 && data[i] != (post[i] % 2)) {
                    System.out.println("VCL " + (i + 1) + " " + (root + 1) + " " + post[i] + " " + count[i] + " " + level[i] + " " + map[i]);

                }
            }

            out.println(re);
            for (int i = 0; i < m; i++) {
                if (!check[i]) {
                    out.println((i + 1));
                    //System.out.println(Arrays.toString(edge[i]));            
                }
            }
            //System.out.println(Arrays.toString(post));

        }
        out.close();
    }

    static int update(int index, int pa, int[][] edge, boolean[] special, int[] level, int[] num, ArrayList<Integer>[] map) {
        int result = special[index] ? 1 : 0;
        for (int i : map[index]) {
            int nxt = nxt(edge[i], index);
            if (nxt != pa) {
                level[nxt] = 1 + level[index];
                result += update(nxt, index, edge, special, level, num, map);
            }
        }
        return num[index] = result;
    }

    static int nxt(int[] edge, int node) {
        return edge[0] == node ? edge[1] : edge[0];
    }

    public static int[] KMP(String val) {
        int i = 0;
        int j = -1;
        int[] result = new int[val.length() + 1];
        result[0] = -1;
        while (i < val.length()) {
            while (j >= 0 && val.charAt(j) != val.charAt(i)) {
                j = result[j];
            }
            j++;
            i++;
            result[i] = j;
        }
        return result;

    }

    public static boolean nextPer(int[] data) {
        int i = data.length - 1;
        while (i > 0 && data[i] < data[i - 1]) {
            i--;
        }
        if (i == 0) {
            return false;
        }
        int j = data.length - 1;
        while (data[j] < data[i - 1]) {
            j--;
        }
        int temp = data[i - 1];
        data[i - 1] = data[j];
        data[j] = temp;
        Arrays.sort(data, i, data.length);
        return true;
    }

    public static int digit(long n) {
        int result = 0;
        while (n > 0) {
            n /= 10;
            result++;
        }
        return result;
    }

    public static double dist(long a, long b, long x, long y) {
        double val = (b - a) * (b - a) + (x - y) * (x - y);
        val = Math.sqrt(val);
        double other = x * x + a * a;
        other = Math.sqrt(other);
        return val + other;

    }

    public static class Point implements Comparable<Point> {

        int x, y;

        public Point(int start, int end) {
            this.x = start;
            this.y = end;
        }

        @Override
        public int hashCode() {
            int hash = 5;
            hash = 47 * hash + this.x;
            hash = 47 * hash + this.y;
            return hash;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final Point other = (Point) obj;
            if (this.x != other.x) {
                return false;
            }
            if (this.y != other.y) {
                return false;
            }
            return true;
        }

        @Override
        public int compareTo(Point o) {
            return Integer.compare(x, o.x);
        }
    }

    public static class FT {

        long[] data;

        FT(int n) {
            data = new long[n];
        }

        public void update(int index, long value) {
            while (index < data.length) {
                data[index] += value;
                index += (index & (-index));
            }
        }

        public long get(int index) {
            long result = 0;
            while (index > 0) {
                result += data[index];
                index -= (index & (-index));
            }
            return result;

        }
    }

    public static long gcd(long a, long b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }

    public static long pow(long a, long b, long MOD) {
        if (b == 0) {
            return 1;
        }
        if (b == 1) {
            return a;
        }
        long val = pow(a, b / 2, MOD);
        if (b % 2 == 0) {
            return val * val % MOD;
        } else {
            return val * (val * a % MOD) % MOD;

        }
    }

    static class Scanner {

        BufferedReader br;
        StringTokenizer st;

        public Scanner() throws FileNotFoundException {
            // System.setOut(new PrintStream(new BufferedOutputStream(System.out), true));
            br = new BufferedReader(new InputStreamReader(System.in));
            //  br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("input.txt"))));
        }

        public String next() {

            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

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

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

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public String nextLine() {
            st = null;
            try {
                return br.readLine();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }

        public boolean endLine() {
            try {
                String next = br.readLine();
                while (next != null && next.trim().isEmpty()) {
                    next = br.readLine();
                }
                if (next == null) {
                    return true;
                }
                st = new StringTokenizer(next);
                return st.hasMoreTokens();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }
    }
}
