#include <bits/stdc++.h>
using namespace std;
template <typename T1, typename T2>
string print_iterable(T1 begin_iter, T2 end_iter, int counter) {
  bool done_something = false;
  stringstream res;
  res << "[";
  for (; begin_iter != end_iter and counter; ++begin_iter) {
    done_something = true;
    counter--;
    res << *begin_iter << ", ";
  }
  string str = res.str();
  if (done_something) {
    str.pop_back();
    str.pop_back();
  }
  str += "]";
  return str;
}
vector<int> SortIndex(int size, std::function<bool(int, int)> compare) {
  vector<int> ord(size);
  for (int i = 0; i < size; i++) ord[i] = i;
  sort(ord.begin(), ord.end(), compare);
  return ord;
}
template <typename T>
bool MinPlace(T& a, const T& b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
bool MaxPlace(T& a, const T& b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename S, typename T>
ostream& operator<<(ostream& out, const pair<S, T>& p) {
  out << "{" << p.first << ", " << p.second << "}";
  return out;
}
template <typename T>
ostream& operator<<(ostream& out, const vector<T>& v) {
  out << "[";
  for (int i = 0; i < (int)v.size(); i++) {
    out << v[i];
    if (i != (int)v.size() - 1) out << ", ";
  }
  out << "]";
  return out;
}
const int MAXN = 300010;
int D[MAXN];
vector<int> aa[MAXN];
vector<int> edge_index[MAXN];
vector<int> chosen;
int N, M;
bool fatto[MAXN];
bool dfs(int v) {
  fatto[v] = true;
  int current_degree = 0;
  for (int i = 0; i < (int)aa[v].size(); i++) {
    int a = aa[v][i];
    if (fatto[a]) continue;
    if (dfs(a)) {
      current_degree++;
      chosen.push_back(edge_index[v][i]);
    }
  }
  if (D[v] != -1 and current_degree % 2 != D[v]) return 1;
  return 0;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N >> M;
  int one_num = 0;
  int minus_index = 0;
  for (int i = 1; i <= N; i++) {
    cin >> D[i];
    if (D[i] == 1) one_num++;
    if (D[i] == -1) minus_index = i;
  }
  if (minus_index == 0 and (one_num % 2)) {
    cout << "-1\n";
    return 0;
  }
  for (int i = 1; i <= M; i++) {
    int a, b;
    cin >> a >> b;
    aa[a].push_back(b);
    edge_index[a].push_back(i);
    aa[b].push_back(a);
    edge_index[b].push_back(i);
  }
  int root = 1;
  if (minus_index) root = minus_index;
  dfs(root);
  cout << chosen.size() << "\n";
  for (int x : chosen) cout << x << "\n";
}
