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.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.util.*;

public class B {
    static int V;
    static HashSet<Edge> adjList[];
    static int[] d;
    static ArrayList<Integer> res = new ArrayList<>();
    static boolean[] blockedEdges;
    static boolean[] visited;
    static int dfs(int node) {
        visited[node] = true;
        ArrayList<Edge> adjacent = new ArrayList<>();
        for (Edge nxt : adjList[node])
            if (!blockedEdges[nxt.idx])
                adjacent.add(nxt);
        for (Edge nxt : adjList[node])
            blockedEdges[nxt.idx] = true;
        
            int cnt = 1;
            for (Edge nxt : adjacent)
                if (!visited[nxt.v])
                    if (dfs(nxt.v) == 1) {
                        res.add(nxt.idx);
                        cnt++;
                    }
            int ret = 0;
            if (cnt % 2 == d[node]) {
                ret = 1;
            }
            return ret;
    }

    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        V = sc.nextInt();
        int m = sc.nextInt();
        adjList = new HashSet[V];
        for (int i = 0; i < V; i++)
            adjList[i] = new HashSet<>();
        blockedEdges = new boolean[m + 1];
        d = new int[V];
        visited = new boolean[V];
        ArrayList<Integer> negIndices = new ArrayList<>();
        int total = 0;
        for (int i = 0; i < V; i++) {
            d[i] = sc.nextInt();
            if (d[i] == -1) negIndices.add(i);
            else total += d[i];
        }

        if (total % 2 == 1 && negIndices.isEmpty()) {
            out.println(-1);
            out.flush();
            return;
        } else if (total % 2 == 1) {
            d[negIndices.get(0)] = 1;
            for (int i = 1; i < negIndices.size(); i++)
                d[negIndices.get(i)] = 0;
        } else {
            for (int i = 0; i < negIndices.size(); i++)
                d[negIndices.get(i)] = 0;
        }

        int[] uu = new int[m], vv = new int[m];
        for (int i = 0; i < m; i++) {
            int u = sc.nextInt() - 1, v = sc.nextInt() - 1;
            uu[i] = u;
            vv[i] = v;
            adjList[u].add(new Edge(v, i));
            adjList[v].add(new Edge(u, i));
        }

        dfs (0);
        out.println(res.size());
        for (int idx : res)
            out.println(idx + 1);

        out.flush();
        out.close();
    }


    static class Edge {
        int v, idx;

        Edge(int vv, int i) {
            v = vv;
            idx = i;
        }
    }


    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

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

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

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public double nextDouble() throws IOException {
            String x = next();
            StringBuilder sb = new StringBuilder("0");
            double res = 0, f = 1;
            boolean dec = false, neg = false;
            int start = 0;
            if (x.charAt(0) == '-') {
                neg = true;
                start++;
            }
            for (int i = start; i < x.length(); i++)
                if (x.charAt(i) == '.') {
                    res = Long.parseLong(sb.toString());
                    sb = new StringBuilder("0");
                    dec = true;
                } else {
                    sb.append(x.charAt(i));
                    if (dec)
                        f *= 10;
                }
            res += Long.parseLong(sb.toString()) / f;
            return res * (neg ? -1 : 1);
        }

        public boolean ready() throws IOException {
            return br.ready();
        }

    }
}