#include <bits/stdc++.h>
using namespace std;
const int MX_N = 3e5 + 5;
const int MX_M = 3e5 + 5;
int N, M, D[MX_N];
vector<pair<int, int>> al[MX_N];
int vis[MX_N], sumD;
vector<int> edges;
void dfs(int u, int p = 0, int pe = 0) {
  vis[u] = 1;
  for (auto v : al[u])
    if (!vis[v.first]) {
      dfs(v.first, u, v.second);
    }
  if (D[u]) edges.push_back(pe), D[p] ^= 1;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> N >> M;
  for (int i = (1); i <= (N); ++i) {
    cin >> D[i];
    if (D[i] >= 0) sumD += D[i];
  }
  for (int i = (1); i <= (M); ++i) {
    int U, V;
    cin >> U >> V;
    al[U].emplace_back(V, i);
    al[V].emplace_back(U, i);
  }
  for (int i = (1); i <= (N); ++i)
    if (D[i] == -1) {
      if (sumD & 1)
        D[i] = 1, ++sumD;
      else
        D[i] = 0;
    }
  if (sumD & 1)
    cout << -1;
  else {
    dfs(1);
    cout << ((int)(edges).size()) << '\n';
    sort(edges.begin(), edges.end());
    for (int& e : edges) cout << e << ' ';
  }
}
