#include <bits/stdc++.h>
using namespace std;
const int maxN = 1e6 + 5, MOD = 1e9 + 9, eps = 1e-7;
int d[maxN];
vector<int> G[maxN], tree[maxN];
int n, m, a, b;
bool vis[maxN];
map<pair<int, int>, int> edgeid;
void dfs(int u) {
  vis[u] = true;
  for (int v : G[u]) {
    if (!vis[v]) {
      tree[u].push_back(v);
      dfs(v);
    }
  }
}
vector<int> ans;
void dfs2(int u, int par) {
  for (int v : tree[u]) {
    dfs2(v, u);
  }
  if (d[u] & 1) {
    if (~par) {
      ans.push_back(edgeid[{u, par}]);
      d[par] = (d[par] + 1) % 2;
    }
  }
}
void print() {
  for (int i = int(0); i < int(n); i++) {
    cout << i << ": ";
    for (int j = int(0); j < int(tree[i].size()); j++) {
      cout << tree[i][j] << " ";
    }
    cout << '\n';
  }
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  int sum = 0;
  for (int i = int(0); i < int(n); i++) {
    cin >> d[i];
    if (~d[i]) sum += d[i];
  }
  for (int i = 0; i < n; i++) {
    if (d[i] == -1) {
      if (sum & 1) {
        d[i] = 1;
        sum++;
      } else {
        d[i] = 0;
      }
    }
  }
  if (sum & 1) {
    cout << -1 << '\n';
    return 0;
  }
  for (int i = int(0); i < int(m); i++) {
    cin >> a >> b, a--, b--;
    edgeid[{a, b}] = edgeid[{b, a}] = i;
    G[a].push_back(b);
    G[b].push_back(a);
  }
  dfs(0);
  dfs2(0, -1);
  cout << ans.size() << '\n';
  sort((ans).begin(), (ans).end());
  for (int x : ans) {
    cout << x + 1 << '\n';
  }
  return 0;
}
