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 maxn = 1000 * 1000 + 10;
const int maxn5 = 3 * 100 * 1000 + 10;
const long long mod = 1000 * 1000 * 1000 + 7;
const long long inf = 1LL * 2 * 1000 * 1000 * 1000 * 1000 * 1000 * 1000 + 10;
vector<pair<int, int> > adj[maxn5];
bool mark[maxn5], ans[maxn5];
int val[maxn5], cnt[maxn5], out = 0;
bool dfs(int v) {
  mark[v] = true;
  for (auto u : adj[v])
    if (!mark[u.first]) {
      if (dfs(u.first)) {
        cnt[v]--;
        ans[u.second] = true;
        out--;
      }
    }
  if (cnt[v] % 2 != val[v]) return 1;
  return 0;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> val[i];
  for (int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    adj[a].push_back(make_pair(b, i + 1));
    adj[b].push_back(make_pair(a, i + 1));
    cnt[a]++;
    cnt[b]++;
  }
  out = m;
  int v = 1;
  for (int i = 1; i <= n; i++)
    if (val[i] == -1) v = i;
  dfs(v);
  if (val[v] != -1 and cnt[v] % 2 != val[v]) return cout << -1 << endl, 0;
  cout << out << endl;
  for (int i = 1; i <= m; i++)
    if (!ans[i]) cout << i << '\n';
  return 0;
}
