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);
}
bool check() {
  bool res = true;
  for (auto i : v)
    if (i != 0) res ^= true;
  return res;
}
void swap() {
  for (int i = 0; i < n; i++)
    if (v[i] == -1) return void(v[i] = 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() {
  d.resize(n, -1);
  p.resize(n, {0, -2});
  DFS(0, 0);
  vector<long long> deg(n, 0);
  for (auto vr : q) {
    if (deg[vr] != v[vr]) {
      deg[vr] ^= 1;
      deg[p[vr].first] ^= 1;
      ans.push_back(p[vr].second);
    }
  }
  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});
  }
  if (!check()) swap();
  if (!check()) bad();
  for (auto &i : v) i = abs(i);
  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;
}
