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

#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 10, LOG = 21;
int in[N], D[N], M[N], P[LOG][N], ps[N], H[N], n, m;
vector<pair<int, int> > adj[N];
pair<int, int> E[N];
void preDFS(int v) {
  M[v] = 1;
  for (pair<int, int> u : adj[v]) {
    if (!M[u.first]) {
      in[u.second] = 1;
      P[0][u.first] = v, H[u.first] = H[v] + 1;
      preDFS(u.first);
    }
  }
}
int getpar(int v, int h) {
  for (int i = h; i; i -= i & -i) {
    v = P[__builtin_ctz(i)][v];
  }
  return v;
}
int LCA(int u, int v) {
  if (H[u] < H[v]) swap(u, v);
  u = getpar(u, H[u] - H[v]);
  if (u == v) return v;
  for (int i = LOG; i--;) {
    if (P[i][v] != P[i][u]) {
      u = P[i][u], v = P[i][v];
    }
  }
  return P[0][v];
}
void DFS(int v) {
  M[v] = 1;
  for (pair<int, int> u : adj[v]) {
    if (!M[u.first]) {
      DFS(u.first);
      ps[v] += ps[u.first];
    }
  }
}
int main() {
  scanf("%d%d", &n, &m);
  vector<int> odd;
  for (int i = 1; i <= n; i++) {
    scanf("%d", &D[i]);
    if (D[i] == 1) odd.push_back(i);
  }
  for (int i = 1; i <= m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    adj[u].push_back({v, i});
    adj[v].push_back({u, i});
    E[i] = {u, v};
  }
  preDFS(1);
  for (int i = 1; i <= n; i++) {
    if (D[i] == -1 && ((int)odd.size() & 1)) odd.push_back(i);
  }
  memset(M, 0, sizeof M);
  if ((int)odd.size() & 1) return !printf("-1\n");
  for (int i = 0; i < (int)odd.size(); i += 2) {
    int p = LCA(odd[i], odd[i + 1]);
    ps[odd[i + 1]]++, ps[odd[i]]++, ps[p] -= 2;
  }
  DFS(1);
  vector<int> ans;
  for (int i = 1; i <= m; i++) {
    int u = E[i].first, v = E[i].second;
    if (H[u] < H[v]) swap(u, v);
    if (in[i] && (ps[u] & 1)) ans.push_back(i);
  }
  printf("%d\n", (int)ans.size());
  for (int x : ans) printf("%d ", x);
  printf("\n");
  return 0;
}
