#include <bits/stdc++.h>
using namespace std;
int par[300005];
int vis[300005];
unordered_map<int, int> edge[300005];
int d[300005];
vector<int> ans;
int find(int u) { return par[u] == u ? u : par[u] = find(par[u]); }
void join(int u, int v) {
  u = find(u);
  v = find(v);
  if (u > v) swap(u, v);
  par[v] = u;
}
void dfs(int u, int pr) {
  if (vis[u]) return;
  vis[u] = 1;
  for (auto i : edge[u]) {
    dfs(i.first, u);
  }
  if (d[u] == 1) {
    ans.push_back(edge[u][pr]);
    d[pr]++;
    d[pr] %= 2;
    return;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  memset(vis, 0, sizeof vis);
  int n, k, u, v;
  cin >> n >> k;
  for (int i = 1; i <= n; i++) {
    edge[i].clear();
    par[i] = i;
    cin >> d[i];
  }
  for (int i = 1; i <= k; i++) {
    cin >> u >> v;
    if (find(u) != find(v)) {
      edge[u][v] = i;
      edge[v][u] = i;
      join(u, v);
    }
  }
  int sum = 0;
  int avail = 0;
  for (int i = 1; i <= n; i++) {
    if (d[i] == -1) {
      avail++;
    } else
      sum += d[i];
  }
  if (sum % 2 && !avail) {
    cout << -1 << endl;
    return 0;
  }
  for (int i = 1; i <= n; i++) {
    if (d[i] == -1) {
      if (sum % 2 == 1) {
        d[i] = 1;
        sum++;
      } else
        d[i] = 0;
    }
  }
  dfs(1, 0);
  cout << ans.size() << endl;
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i] << " ";
  }
  return 0;
}
