#include <bits/stdc++.h>
using namespace std;
long long t, n, m, u, v, q, k;
const int N = 3e5 + 500;
const int LN = 20;
const int SN = 331;
const long long mod = 1e9 + 7;
const long long INF = 1LL << 57;
long long arr[N], brr[N];
string str, ss;
vector<int> adj[N];
vector<int> idx[N];
int d[N];
int actuald[N];
bool can[N];
bool vis[N];
void dfs(int v, int p) {
  if (d[v] == -1) d[v] = 0;
  vis[v] = true;
  for (int i = 0; i < adj[v].size(); ++i) {
    int u = adj[v][i];
    if (u == p || vis[u]) continue;
    dfs(u, v);
    if (actuald[u] != d[u]) {
      can[idx[v][i]] = true;
      actuald[v]++;
      actuald[u]++;
      actuald[v] %= 2;
      actuald[u] %= 2;
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> m;
  int has = -1, sum = 0;
  for (int i = 1; i <= n; ++i) {
    cin >> d[i];
    if (d[i] == -1)
      has = i;
    else
      sum += d[i];
  }
  for (int i = 1; i <= m; ++i) {
    cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
    idx[u].push_back(i);
    idx[v].push_back(i);
  }
  if (sum % 2 == 1 && has == -1) {
    cout << -1 << '\n';
    return 0;
  }
  if (sum % 2 == 1) d[has] = 1;
  dfs(1, 0);
  sum = 0;
  for (int i = 1; i <= m; ++i) {
    sum += can[i];
  }
  cout << sum << '\n';
  for (int i = 1; i <= m; ++i) {
    if (can[i]) cout << i << " ";
  }
  cout << '\n';
}
