#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 10;
const int MAX_V = 500 + 10;
const int MOD = 1e9 + 7;
int d[maxn];
std::vector<pair<int, int> > G[maxn];
std::vector<int> ans;
bool vis[maxn];
bool dfs(int u) {
  vis[u] = 1;
  for (auto e : G[u]) {
    if (vis[e.first]) continue;
    if (dfs(e.first)) {
      ans.push_back(e.second);
      d[e.first] ^= 1;
      d[u] ^= 1;
    }
  }
  return d[u];
}
int main() {
  ios_base::sync_with_stdio(0);
  cout.tie(0);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  int ok = 0;
  int root = -1;
  for (int i = 1; i <= n; ++i) {
    cin >> d[i];
    if (d[i] == -1)
      root = i;
    else
      ok ^= d[i];
  }
  for (int i = 1; i <= m; ++i) {
    int u, v;
    cin >> u >> v;
    G[u].push_back(make_pair(v, i));
    G[v].push_back(make_pair(u, i));
  }
  if (ok && root == -1) {
    std::cout << "-1" << '\n';
    return 0;
  }
  if (ok)
    d[root] = 1;
  else
    root = 1;
  for (int i = 1; i <= n; ++i) {
    if (d[i] == -1) d[i] = 0;
  }
  memset((vis), (0), sizeof(vis));
  dfs(root);
  std::cout << ans.size() << '\n';
  for (auto id : ans) {
    std::cout << id << '\n';
  }
  return 0;
}
