#include <bits/stdc++.h>
using namespace std;
template <typename T>
void out(T x) {
  cout << x << endl;
  exit(0);
}
const int maxn = 1e6 + 11;
int n;
int m;
int d[maxn];
set<pair<int, int>> g[maxn];
int sum = 0;
int negs = 0;
vector<bool> seen(maxn, false);
vector<int> ans;
int dfs(int u, int idx) {
  seen[u] = true;
  int c = d[u];
  for (auto p : g[u]) {
    int v = p.first;
    if (!seen[v] && dfs(v, p.second)) {
      c ^= 1;
    }
  }
  if (c) {
    ans.push_back(idx);
  }
  return c;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    cin >> d[i];
    if (d[i] == -1) {
      negs++;
    } else {
      sum += d[i];
    }
  }
  if (sum % 2 && negs == 0) out(-1);
  for (int i = 1; i <= n; i++) {
    if (d[i] == -1) {
      if (sum % 2) {
        d[i] = 1;
        sum++;
      } else {
        d[i] = 0;
      }
    }
  }
  for (int i = 1; i <= m; i++) {
    int u, v;
    cin >> u >> v;
    g[u].insert(make_pair(v, i));
    g[v].insert(make_pair(u, i));
  }
  dfs(1, -1);
  cout << ans.size() << "\n";
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i];
    cout << ((i < ans.size() - 1) ? " " : "\n");
  }
  return 0;
}
