#include <bits/stdc++.h>
using namespace std;
const int MAXN = int(3e5);
const int MAXM = int(3e5);
int N, M;
int D[MAXN];
int U[MAXM], V[MAXM];
int fa[MAXN];
int find(int x) { return fa[x] == x ? x : fa[x] = find(fa[x]); }
int unite(int x, int y) {
  int a = find(x), b = find(y);
  if (a == b) return 0;
  return fa[a] = b, 1;
}
vector<pair<int, int>> G[MAXN];
vector<int> ans;
int curd[MAXN];
void dfs(int u, int fa, int eid) {
  for (auto p : G[u]) {
    if (p.first == fa) continue;
    dfs(p.first, u, p.second);
  }
  if (curd[u] != D[u] && fa != -1) {
    curd[u] ^= 1;
    curd[fa] ^= 1;
    ans.emplace_back(eid);
  }
}
signed main() {
  ios::sync_with_stdio(false);
  cin >> N >> M;
  int root = 0;
  for (int i = 0; i < N; ++i) {
    cin >> D[i];
    if (D[i] == -1) root = i;
  }
  for (int i = 0; i < M; ++i) {
    cin >> U[i] >> V[i];
    --U[i], --V[i];
  }
  for (int i = 0; i < N; ++i) {
    fa[i] = i;
  }
  for (int i = 0; i < M; ++i) {
    if (unite(U[i], V[i])) {
      G[U[i]].emplace_back(V[i], i);
      G[V[i]].emplace_back(U[i], i);
    }
  }
  dfs(root, -1, -1);
  for (int i = 0; i < N; ++i) {
    if (D[i] == -1) continue;
    if (curd[i] != D[i]) {
      cout << -1 << endl;
      exit(0);
    }
  }
  cout << ans.size() << "\n";
  for (size_t i = 0; i < ans.size(); ++i) {
    cout << ans[i] + 1 << "\n";
  }
  return 0;
}
