#include <bits/stdc++.h>
using namespace std;
int n, m;
vector<int> d;
vector<vector<pair<int, int> > > g;
vector<bool> b;
set<int> ans;
bool dfs1(int v) {
  if (b[v]) return false;
  b[v] = true;
  int deg = 0;
  for (pair<int, int> i : g[v])
    if (dfs1(i.second)) {
      ans.insert(i.first);
      deg = (deg + 1) % 2;
    }
  if (d[v] >= 0 && d[v] != deg)
    return true;
  else
    return false;
}
int dfs2(int v) {
  if (b[v]) return 0;
  b[v] = true;
  int res = 0;
  for (pair<int, int> i : g[v]) {
    int p = dfs2(i.second);
    res += p;
    if (p % 2 == 1) ans.insert(i.first);
  }
  if (d[v] == 1) res++;
  return res;
}
int main() {
  cin >> n >> m;
  d.resize(n);
  int dm1 = -1;
  set<int> d1;
  for (int i = 0; i < n; i++) {
    cin >> d[i];
    if (d[i] == -1) dm1 = i;
    if (d[i] == 1) d1.insert(i);
  }
  g.resize(n);
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    u--;
    v--;
    g[u].push_back(make_pair(i, v));
    g[v].push_back(make_pair(i, u));
  }
  if ((dm1 == -1) && (int(d1.size()) % 2 == 1)) cout << -1, exit(0);
  b = vector<bool>(n);
  if (dm1 != -1)
    dfs1(dm1);
  else if (!d1.empty())
    dfs1(*d1.begin());
  cout << int(ans.size()) << "\n";
  for (int k : ans) cout << k + 1 << "\n";
}
