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.util.*;
import java.io.*;
import java.text.*;

public class Gymaya {
    static class Edge implements Comparable<Edge>{
        int u,v,idx;
        Edge(int a,int b,int c){
            u=a;
            v=b;
            idx=c;
        }

        @Override
        public int compareTo(Edge edge) {
            if (u==edge.u)return v-edge.v;
            return u-edge.u;
        }
    }
    static ArrayList<Integer>[]adj;
    static ArrayList<Integer>sol;
    static boolean[]vis;
    static int []cur,a;
    static TreeSet<Edge>ts;
    static void dfs(int u){
        vis[u]=true;
        for (int v:adj[u]){
            if (!vis[v]){
                dfs(v);
                if (cur[v]!=a[v]){
                    sol.add(ts.ceiling(new Edge(Math.min(u,v),Math.max(u,v),0)).idx);
                    cur[u]++;
                }
            }
        }
        cur[u]%=2;
    }
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        int n = sc.nextInt();
        int m = sc.nextInt();
        a= new int[n];
        boolean is=false;
        int s = 0;
        for (int i =0;i<n;i++){
            a[i]=sc.nextInt();
            if (a[i]==-1)is=true;
            else s+=a[i]%2;
        }
        adj= new ArrayList[n];
        for (int i =0;i<n;i++)adj[i]=new ArrayList<>();
        s%=2;
        if (!is&&s%2==1){
            pw.println(-1);
        }
        else {
            for (int i =0;i<n;i++){
                if (a[i]==-1){
                    if (s==1){
                        s=0;
                        a[i]=1;
                    }else a[i]=0;
                }
            }
            int k=1;
            ts= new TreeSet<>();
            while (m-->0){
                int u = sc.nextInt()-1;
                int v = sc.nextInt()-1;
                ts.add(new Edge(Math.min(u,v),Math.max(u,v),k));
                adj[u].add(v);
                adj[v].add(u);
                k++;
            }
            sol= new ArrayList<>();
            vis= new boolean[n];
            cur= new int[n];
            dfs(0);
            pw.println(sol.size());
            for (int x:sol){
                pw.print(x+" ");
            }
        }


        pw.flush();
    }
    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(FileReader r) {
            br = new BufferedReader(r);
        }

        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();
        }
    }


}