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;
int N, M;
vector<pair<int, int> > G[300005];
int D[300005];
bool vis[300005];
vector<int> ans;
void dfs(int u, int p = -1, int eid = -1) {
  vis[u] = true;
  for (pair<int, int> e : G[u]) {
    int v = e.first, id = e.second;
    if (vis[v]) continue;
    dfs(v, u, id);
  }
  if (D[u] == 1) {
    assert(p != -1);
    D[p] = !D[p];
    ans.push_back(eid);
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N >> M;
  int od = 0, ne = 0;
  for (int i = 1; i <= N; i++) {
    cin >> D[i];
    if (D[i] == 1) od++;
    if (D[i] == -1) ne++;
  }
  int u, v;
  for (int i = 1; i <= M; i++) {
    cin >> u >> v;
    G[u].push_back(make_pair(v, i));
    G[v].push_back(make_pair(u, i));
  }
  if ((od & 1) && ne == 0) {
    cout << -1 << '\n';
    return 0;
  }
  bool chg = !(od & 1);
  for (int i = 1; i <= N; i++) {
    if (D[i] == -1) {
      if (!chg) {
        chg = true;
        D[i] = 1;
      } else
        D[i] = 0;
    }
  }
  dfs(1);
  cout << ans.size() << '\n';
  for (int ai : ans) cout << ai << '\n';
  return 0;
}
