#include <bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;
struct rng {
  struct A {
    int n;
    const bool operator!=(A r) { return n != r.n; }
    A& operator++() {
      n++;
      return *this;
    }
    int operator*() { return n; }
  };
  int l, r;
  rng(int r) : l(0), r(r) {}
  rng(int l, int r) : l(l), r(r) {}
  A begin() { return A{l}; }
  A end() { return A{r}; }
};
const int MN = 300300;
struct E {
  int to, id;
};
int n, m;
V<E> g[MN];
int d[MN];
bool used[MN] = {};
V<int> res;
int dfs(int p) {
  used[p] = true;
  int sm = d[p];
  for (auto e : g[p]) {
    int d = e.to;
    if (used[d]) continue;
    if (dfs(d)) {
      res.push_back(e.id);
      sm = 1 - sm;
    }
  }
  return sm;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(20);
  cin >> n >> m;
  int sm = 0;
  int sp = -1;
  for (int i : rng(n)) {
    cin >> d[i];
    if (d[i] == -1) {
      if (sp == -1) {
        sp = i;
        continue;
      }
      d[i] = 0;
    }
    sm += d[i];
    sm %= 2;
  }
  if (sm && sp == -1) {
    cout << -1 << endl;
    return 0;
  }
  d[sp] = sm;
  for (int i : rng(m)) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    g[a].push_back(E{b, i + 1});
    swap(a, b);
    g[a].push_back(E{b, i + 1});
  }
  dfs(0);
  cout << res.size() << endl;
  for (int d : res) {
    cout << d << endl;
  }
  return 0;
}
