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 + 5;
unordered_set<int> adj[N];
unordered_map<int, unordered_map<int, int>> mp;
int D[N], idx = -1, odd = 0;
bool vis[N], marked[N];
void dfs(int u) {
  if (vis[u]) return;
  vis[u] = true;
  auto tmp = adj[u];
  if (D[u] == 1 && !marked[u] && (int)adj[u].size() % 2 == 0) {
    auto it = adj[u].begin();
    if (vis[*it]) it++;
    adj[u].erase(it);
    adj[*it].erase(u);
    D[*it] = 1 - D[*it];
  }
  for (int v : tmp) dfs(v);
}
int main() {
  ios::sync_with_stdio(0);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i < int(n + 1); i++) {
    cin >> D[i];
    if (D[i] == -1) idx = i;
    odd += (D[i] == 1);
  }
  if (odd % 2 && idx == -1) {
    cout << -1;
  } else {
    if (odd % 2) D[idx] = 1;
    for (int i = 0; i < int(m); i++) {
      int u, v;
      cin >> u >> v;
      adj[u].insert(v);
      adj[v].insert(u);
      mp[u][v] = mp[v][u] = i + 1;
    }
    unordered_set<int> ans;
    for (int i = 1; i < int(n + 1); i++)
      if (D[i] == 1) {
        bool bad = true;
        for (int v : adj[i])
          if (D[v] == 1) bad = false;
        if (bad) {
          int w = *adj[i].begin();
          ans.insert(mp[i][w]);
          D[w] = 1;
          marked[i] = true;
        }
      }
    dfs(1);
    for (int i = 1; i < int(n + 1); i++)
      if (!marked[i])
        for (int v : adj[i]) ans.insert(mp[i][v]);
    cout << ans.size() << '\n';
    for (int i : ans) cout << i << '\n';
  }
  return 0;
}
