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.List;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.Comparator;
import java.util.Collections;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Pradyumn Agrawal coderbond007  PLEASE!! PLEASE!! HACK MY SOLUTION!!
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastReader in = new FastReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskD solver = new TaskD();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskD {
        public void solve(int testNumber, FastReader in, PrintWriter out) {
            int n = in.nextInt();
            int m = in.nextInt();
            TaskD.Vertex[] v = new TaskD.Vertex[n];
            for (int i = 0; i < n; ++i) v[i] = new TaskD.Vertex(in.nextInt());
            for (int i = 0; i < m; ++i) {
                TaskD.Vertex a = v[in.nextInt() - 1];
                TaskD.Vertex b = v[in.nextInt() - 1];
                a.outgo.add(new TaskD.Edge(b, i + 1));
                b.outgo.add(new TaskD.Edge(a, i + 1));
            }
            TaskD.Vertex root = v[0];
            for (TaskD.Vertex vv : v)
                if (vv.d < 0) {
                    root = vv;
                    break;
                }
            List<TaskD.Edge> answer = new ArrayList<>();
            root.dfs(answer);
            if (root.d >= 0 && root.d != root.got) {
                out.println(-1);
            } else {
                out.println(answer.size());
                Collections.sort(answer, Comparator.comparingInt(o -> o.index));
                for (TaskD.Edge e : answer) {
                    out.println(e.index);
                }
            }
        }

        static class Edge {
            TaskD.Vertex dest;
            int index;

            public Edge(TaskD.Vertex dest, int index) {
                this.dest = dest;
                this.index = index;
            }

        }

        static class Vertex {
            int d;
            int got = -1;
            List<TaskD.Edge> outgo = new ArrayList<>();

            public Vertex(int d) {
                this.d = d;
            }

            public void dfs(List<TaskD.Edge> answer) {
                got = 0;
                for (TaskD.Edge e : outgo)
                    if (e.dest.got < 0) {
                        e.dest.dfs(answer);
                        if (e.dest.d >= 0 && e.dest.d != e.dest.got) {
                            answer.add(e);
                            e.dest.got ^= 1;
                            got ^= 1;
                        }
                    }
            }

        }

    }

    static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[8192];
        private int curChar;
        private int pnumChars;
        private FastReader.SpaceCharFilter filter;

        public FastReader(InputStream stream) {
            this.stream = stream;
        }

        private int pread() {
            if (pnumChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= pnumChars) {
                curChar = 0;
                try {
                    pnumChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (pnumChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int nextInt() {
            int c = pread();
            while (isSpaceChar(c))
                c = pread();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = pread();
            }
            int res = 0;
            do {
                if (c == ',') {
                    c = pread();
                }
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = pread();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        private boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        private static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }
}

