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;
string DBG_DLM(int& i) { return (i++ == 0 ? "" : ", "); }
template <class T>
ostream& operator<<(ostream& os, vector<T> v);
template <class T>
ostream& operator<<(ostream& os, set<T> v);
template <class T>
ostream& operator<<(ostream& os, queue<T> q);
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q);
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p);
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> mp);
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> mp);
template <int I, class TPL>
void DBG(ostream& os, TPL t) {}
template <int I, class TPL, class H, class... Ts>
void DBG(ostream& os, TPL t) {
  os << (I == 0 ? "" : ", ") << get<I>(t);
  DBG<I + 1, TPL, Ts...>(os, t);
}
template <class T, class K>
void DBG(ostream& os, pair<T, K> p, string delim) {
  os << "(" << p.first << delim << p.second << ")";
}
template <class... Ts>
ostream& operator<<(ostream& os, tuple<Ts...> t) {
  os << "(";
  DBG<0, tuple<Ts...>, Ts...>(os, t);
  os << ")";
  return os;
}
template <class T, class K>
ostream& operator<<(ostream& os, pair<T, K> p) {
  DBG(os, p, ", ");
  return os;
}
template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : v) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, set<T> s) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& t : s) {
        os << DBG_DLM(i) << t;
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.front();
      };
    }
    os << "}";
    return os;
  };
}
template <class T>
ostream& operator<<(ostream& os, priority_queue<T> q) {
  {
    int i = 0;
    os << "{";
    {
      for (; q.size(); q.pop()) {
        os << DBG_DLM(i) << q.top();
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
template <class T, class K>
ostream& operator<<(ostream& os, unordered_map<T, K> m) {
  {
    int i = 0;
    os << "{";
    {
      for (auto&& p : m) {
        os << DBG_DLM(i);
        DBG(os, p, "->");
      };
    }
    os << "}";
    return os;
  };
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using vs = vector<string>;
using vvs = vector<vs>;
using vvvs = vector<vvs>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vvvb = vector<vvb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vvvd = vector<vvd>;
using vpii = vector<pii>;
using vvpii = vector<vpii>;
using vvvpii = vector<vvpii>;
template <class A, class B>
bool amax(A& a, const B& b) {
  return b > a ? a = b, 1 : 0;
}
template <class A, class B>
bool amin(A& a, const B& b) {
  return b < a ? a = b, 1 : 0;
}
ll ri() {
  ll l;
  cin >> l;
  return l;
}
string rs() {
  string s;
  cin >> s;
  return s;
}
void panic() {
  cout << -1 << endl;
  exit(0);
}
using Weight = int;
struct Edge {
  int dst;
  int idx;
  int used;
  Weight weight;
  Edge(int d, int idx) : dst(d), idx(idx), used(0) {}
};
using Edges = vector<Edge>;
using Graph = vector<Edges>;
void Main() {
  int n = ri();
  int m = ri();
  vector<int> D(n);
  for (int i = int(0); i < int(n); ++i) D[i] = ri();
  vi dig(n);
  Graph G(n);
  for (int i = int(0); i < int(m); ++i) {
    int u = ri() - 1;
    int v = ri() - 1;
    G[u].emplace_back(v, i);
    G[v].emplace_back(u, i);
    dig[u]++;
    dig[v]++;
  }
  map<int, vi> dd;
  for (int i = int(0); i < int(n); ++i) {
    dd[dig[i]].emplace_back(i);
  }
  priority_queue<pii> must;
  for (int i = int(0); i < int(n); ++i) {
    if (D[i] == 1) must.emplace(dig[i], i);
  };
  while (!must.empty()) {
    int u = must.top().second;
    must.pop();
    if (D[u] == 0 || D[u] == -1) continue;
    bool ok = 0;
    for (auto&& e : G[u])
      if (e.used == 0) {
        ok = 1;
        int v = e.dst;
        dig[u]--;
        e.used = 1;
        if (D[v] != -1) {
          D[v] = 1 - D[v];
          dig[v]--;
          if (D[v] == 1) {
            must.emplace(dig[v], v);
          }
        }
        break;
      }
    if (!ok) panic();
  }
  vi ans;
  for (int u = int(0); u < int(n); ++u)
    for (auto&& e : G[u])
      if (e.used) {
        ans.emplace_back(e.idx + 1);
      }
  sort((ans).begin(), (ans).end());
  ans.erase(unique(ans.begin(), ans.end()), ans.end());
  int size = ((int)(ans).size());
  cout << size << endl;
  for (int i = int(0); i < int(((int)(ans).size())); ++i) {
    cout << ans[i];
    if (i + 1 < ((int)(ans).size()))
      cout << ' ';
    else
      cout << endl;
  }
}
signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  Main();
  return 0;
}
