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.io.IOException;
import java.io.BufferedReader;
import java.io.Reader;
import java.io.InputStreamReader;
import java.util.TreeSet;
import java.util.ArrayList;
import java.io.InputStream;

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

    static class TaskB {
        int n;
        int m;
        int[] vis;
        int[] st;
        int[] prev;
        int[] rem;
        int[] d;
        int[][] es;
        List<Integer>[] edge;
        TreeSet<Integer> used = new TreeSet<>();

        public void solve(int testNumber, MyInput in, PrintWriter out) {
            n = in.nextInt();
            m = in.nextInt();
            d = in.nextIntArray(n);
            edge = new List[n];
            es = new int[m][];
            for (int i = 0; i < n; i++) edge[i] = new ArrayList<>();
            for (int i = 0; i < m; i++) {
                int a = in.nextInt() - 1;
                int b = in.nextInt() - 1;
                es[i] = new int[]{a, b,};
                edge[a].add(i);
                edge[b].add(i);
            }
            prev = new int[n];
            rem = new int[n];
            vis = new int[n];
            st = new int[n];
            if (!dfs(0)) {
                out.println(-1);
                return;
            }
            out.println(used.size());
            for (int e : used) out.println(e + 1);
        }

        boolean dfs(int r) {
            int sp = 0;
            st[sp++] = r;
            vis[r]++;
            prev[r] = -1;
            rem[r] = -1;
            int cnt1 = 0;
            for (int x : d) if (x == 1) cnt1++;
            cnt1 %= 2;
            while (sp > 0) {
                int v = st[--sp];
                if (vis[v] == 1) {
                    st[sp++] = v;
                    vis[v]++;
                    for (int e : edge[v]) {
                        int t = to(v, e);
                        if (vis[t] == 0) {
                            prev[t] = e;
                            vis[t]++;
                            st[sp++] = t;
                        }
                    }
                } else {
                    int cur = d[v] == 1 || d[v] == -1 && cnt1 == 1 ? v : -1;
                    if (d[v] == -1) cnt1 = 0;
                    for (int e : edge[v]) {
                        int t = to(v, e);
                        if (prev[t] != e) continue;
                        if (rem[t] == -1) continue;
                        if (cur != -1) {
                            path(rem[t], v);
                            path(cur, v);
                            cur = -1;
                        } else cur = rem[t];
                    }
                    rem[v] = cur;
                }
            }
            return rem[r] == -1;
        }

        void path(int t, int v) {
            while (v != t) {
                used.add(prev[t]);
                t = to(t, prev[t]);
            }
        }

        int to(int v, int e) {
            return es[e][es[e][0] == v ? 1 : 0];
        }

    }

    static class MyInput {
        private final BufferedReader in;
        private static int pos;
        private static int readLen;
        private static final char[] buffer = new char[1024 * 8];
        private static char[] str = new char[500 * 8 * 2];
        private static boolean[] isDigit = new boolean[256];
        private static boolean[] isSpace = new boolean[256];
        private static boolean[] isLineSep = new boolean[256];

        static {
            for (int i = 0; i < 10; i++) {
                isDigit['0' + i] = true;
            }
            isDigit['-'] = true;
            isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true;
            isLineSep['\r'] = isLineSep['\n'] = true;
        }

        public MyInput(InputStream is) {
            in = new BufferedReader(new InputStreamReader(is));
        }

        public int read() {
            if (pos >= readLen) {
                pos = 0;
                try {
                    readLen = in.read(buffer);
                } catch (IOException e) {
                    throw new RuntimeException();
                }
                if (readLen <= 0) {
                    throw new MyInput.EndOfFileRuntimeException();
                }
            }
            return buffer[pos++];
        }

        public int nextInt() {
            int len = 0;
            str[len++] = nextChar();
            len = reads(len, isSpace);
            int i = 0;
            int ret = 0;
            if (str[0] == '-') {
                i = 1;
            }
            for (; i < len; i++) ret = ret * 10 + str[i] - '0';
            if (str[0] == '-') {
                ret = -ret;
            }
            return ret;
        }

        public char nextChar() {
            while (true) {
                final int c = read();
                if (!isSpace[c]) {
                    return (char) c;
                }
            }
        }

        int reads(int len, boolean[] accept) {
            try {
                while (true) {
                    final int c = read();
                    if (accept[c]) {
                        break;
                    }
                    if (str.length == len) {
                        char[] rep = new char[str.length * 3 / 2];
                        System.arraycopy(str, 0, rep, 0, str.length);
                        str = rep;
                    }
                    str[len++] = (char) c;
                }
            } catch (MyInput.EndOfFileRuntimeException e) {
            }
            return len;
        }

        public int[] nextIntArray(final int n) {
            final int[] res = new int[n];
            for (int i = 0; i < n; i++) {
                res[i] = nextInt();
            }
            return res;
        }

        static class EndOfFileRuntimeException extends RuntimeException {
        }

    }
}

