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.*;
import java.math.BigInteger;
import java.util.*;

public class Template implements Runnable {

    BufferedReader in;
    PrintWriter out;
    StringTokenizer tok = new StringTokenizer("");

    void init() throws FileNotFoundException {
        try {
            in = new BufferedReader(new FileReader("input.txt"));
            out = new PrintWriter("output.txt");
        } catch (Exception e) {
            String filename = "";
            if (filename.isEmpty()) {
                in = new BufferedReader(new InputStreamReader(System.in));
                out = new PrintWriter(System.out);
            } else {
                in = new BufferedReader(new FileReader(filename + ".in"));
                out = new PrintWriter(filename + ".out");
            }
        }
    }

    String readString() throws IOException {
        while (!tok.hasMoreTokens()) {
            try {
                tok = new StringTokenizer(in.readLine(), " :");
            } catch (Exception e) {
                return null;
            }
        }
        return tok.nextToken();
    }

    int readInt() throws IOException {
        return Integer.parseInt(readString());
    }

    int[] readIntArray(int size) throws IOException {
        int[] res = new int[size];
        for (int i = 0; i < size; i++) {
            res[i] = readInt();
        }
        return res;
    }

    long readLong() throws IOException {
        return Long.parseLong(readString());
    }

    double readDouble() throws IOException {
        return Double.parseDouble(readString());
    }

    <T> List<T>[] createGraphList(int size) {
        List<T>[] list = new List[size];
        for (int i = 0; i < size; i++) {
            list[i] = new ArrayList<>();
        }
        return list;
    }

    public static void main(String[] args) {
        new Template().run();
        //new Thread(null, new Template(), "", 1l * 200 * 1024 * 1024).start();
    }

    long timeBegin, timeEnd;

    void time() {
        timeEnd = System.currentTimeMillis();
        System.err.println("Time = " + (timeEnd - timeBegin));
    }

    long memoryTotal, memoryFree;

    void memory() {
        memoryFree = Runtime.getRuntime().freeMemory();
        System.err.println("Memory = " + ((memoryTotal - memoryFree) >> 10)
                + " KB");
    }

    public void run() {
        try {
            timeBegin = System.currentTimeMillis();
            memoryTotal = Runtime.getRuntime().freeMemory();
            init();
            solve();
            out.close();
            if (System.getProperty("ONLINE_JUDGE") == null) {
                time();
                memory();
            }
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(-1);
        }
    }

    class Edge {
        int to, index;

        public Edge(int to, int index) {
            this.to = to;
            this.index = index;
        }
    }

    List<Edge>[] graph;
    boolean[] triggerToUp;

    List<Integer> answer = new ArrayList<>();
    boolean[] vis;

    boolean dfs(int x, int p) {
        vis[x] = true;
        boolean shouldTrigger = triggerToUp[x];
        for (Edge e : graph[x]) {
            if (e.to == p || vis[e.to]) continue;
            boolean down = dfs(e.to, x);
            if (down) {
                answer.add(e.index);
            }
            shouldTrigger ^= down;
        }
        return shouldTrigger;
    }

    void solve() throws IOException {
        int n = readInt();
        int m = readInt();
        int[] d = readIntArray(n);
        triggerToUp = new boolean[n];
        vis = new boolean[n];
        graph = new List[n];
        for (int i = 0; i < n; i++) {
            graph[i] = new ArrayList<>();
        }
        for (int i = 0; i < m; i++) {
            int x = readInt() - 1;
            int y = readInt() - 1;
            graph[x].add(new Edge(y, i));
            graph[y].add(new Edge(x, i));
        }
        int minusOneIndex = -1;
        for (int i = 0; i < n; i++) {
            if (d[i] == -1) {
                minusOneIndex = i;
            }
        }

        int prevOne = -1;
        for (int i = 0; i < n; i++) {
            if (d[i] == 1) {
                if (minusOneIndex >= 0) {
                    triggerToUp[minusOneIndex] ^= true;
                    triggerToUp[i] ^= true;
                    continue;
                }
                if (prevOne == -1) {
                    prevOne = i;
                } else {
                    triggerToUp[prevOne] ^= true;
                    triggerToUp[i] ^= true;
                    prevOne = -1;
                }
            }
        }
        if (prevOne != -1) {
            out.println(-1);
            return;
        }
        dfs(0, 0);
        out.println(answer.size());
        Collections.sort(answer);
        for (int x : answer) {
            out.println(x + 1);
        }
    }


}