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.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
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);
        TaskB solver = new TaskB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskB {
        int[] firstEdge;
        int[] edgeDst;
        int[] edgeNxt;
        int numEdges;
        boolean[] was;
        boolean[] ans;
        int[] d;

        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            int n = in.nextInt();
            int m = in.nextInt();
            initGraph(n, m);
            d = new int[n];
            int numOdd = 0;
            for (int i = 0; i < n; i++) {
                d[i] = in.nextInt();
                if (d[i] == 1) {
                    ++numOdd;
                }
            }
            int[] s = new int[n];
            Arrays.fill(s, -1);
            for (int i = 0; i < m; i++) {
                int a = in.nextInt() - 1;
                int b = in.nextInt() - 1;
                if (d[a] < 0 && d[b] >= 0) {
                    s[b] = i;
                }
                if (d[b] < 0 && d[a] >= 0) {
                    s[a] = i;
                }
                addEdge(a, b);
                addEdge(b, a);
            }
            ans = new boolean[m];
            if (numOdd % 2 == 1) {
                boolean found = false;
                for (int i = 0; i < n; i++) {
                    if (d[i] == 1 && s[i] >= 0) {
                        found = true;
                        d[i] = 0;
                        ans[s[i]] ^= true;
                        break;
                    }
                }
                if (!found) {
                    out.println(-1);
                    return;
                }
            }
            was = new boolean[n];
            dfs(0);
            int ansSize = 0;
            for (int i = 0; i < m; i++) {
                if (ans[i]) {
                    ++ansSize;
                }
            }
            out.println(ansSize);
            ansSize = 0;
            for (int i = 0; i < m; i++) {
                if (ans[i]) {
                    if (ansSize > 0) {
                        out.print(" ");
                    }
                    out.print(i + 1);
                    ++ansSize;
                }
            }
            out.println();
        }

        private int dfs(int v) {
            was[v] = true;
            int numOdd = 0;
            if (d[v] == 1) {
                ++numOdd;
            }
            for (int e = firstEdge[v]; e >= 0; e = edgeNxt[e]) {
                int u = edgeDst[e];
                if (was[u]) {
                    continue;
                }
                int o = dfs(u);
                numOdd += o;
                if (o % 2 == 1) {
                    ans[e >> 1] ^= true;
                }
            }
            return numOdd;
        }

        private void initGraph(int n, int m) {
            firstEdge = new int[n];
            Arrays.fill(firstEdge, -1);
            edgeDst = new int[2 * m];
            edgeNxt = new int[2 * m];
            numEdges = 0;
        }

        private void addEdge(int a, int b) {
            int e = numEdges++;
            edgeNxt[e] = firstEdge[a];
            edgeDst[e] = b;
            firstEdge[a] = e;
        }

    }

    static class FastScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public FastScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(in.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

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

    }
}

