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>
#pragma GCC optimize("O3", "unroll-all-loops")
#pragma GCC target("avx2")
using namespace std;
ifstream in;
ofstream out;
const long long kk = 1000;
const long long ml = kk * kk;
const long long mod = 998244353;
const long long inf = ml * ml * ml + 7;
long long n, m;
vector<vector<pair<long long, long long>>> e;
vector<long long> v, d, ans, x, q;
vector<pair<long long, long long>> p;
bool viv = false;
void bad() {
  cout << -1;
  exit(0);
}
void DFS(long long v, long long c) {
  d[v] = c;
  for (auto s : e[v])
    if (d[s.first] == -1) DFS(s.first, c + 1), p[s.first] = {v, s.second};
  q.push_back(v);
}
void build() {
  vector<long long> ones;
  long long root = 0;
  d.clear();
  d.resize(n, -1);
  p.resize(n, {root, -2});
  DFS(root, 0);
  for (int i = 0; i < n; i++)
    if (v[i] == 1) ones.push_back(i);
  vector<pair<long long, long long>> pr;
  for (int i = 0; i < ones.size(); i += 2) pr.push_back({ones[i], ones[i + 1]});
  x.resize(n, 0);
  for (auto &p : pr) {
    if (d[p.first] > d[p.second]) swap(p.first, p.second);
    if (viv) cout << p.first << ' ' << p.second << endl;
    x[p.first] = true;
    x[p.second] = true;
    if (viv) cout << "end" << endl;
  }
  if (viv) cout << "ok" << endl;
  vector<long long> deg(n, 0);
  for (auto v : q) {
    if (viv) cout << "Check " << v << endl;
    if (x[v] != deg[v]) {
      ans.push_back(p[v].second);
      deg[v] ^= 1;
      deg[p[v].first] ^= 1;
    }
  }
  cout << ans.size() << endl;
  for (auto i : ans) cout << i + 1 << ' ';
}
void solve() {
  cin >> n >> m;
  v.resize(n);
  for (auto &i : v) cin >> i;
  e.resize(n);
  for (int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    e[a].push_back({b, i});
    e[b].push_back({a, i});
  }
  int root = -1;
  for (int i = 0; i < n; i++)
    if (v[i] == -1) root = i;
  long long sum = 0;
  for (int i = 0; i < root; i++) {
    if (v[i] == -1) v[i] == 1;
  }
  for (int i = 0; i < n; i++)
    if (i != root) sum += v[i];
  if (sum & 1)
    v[root] = 1;
  else
    v[root] = 0;
  sum = 0;
  for (auto i : v) sum += i;
  if (sum & 1) bad();
  build();
}
int main() {
  srand(time(0));
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) solve();
  return 0;
}
