#include <bits/stdc++.h>
using namespace std;
const int mod = 1000000007;
vector<pair<int, int> > g[300100];
int ans[300100];
int s[300100];
int d[300100];
bool used[300100];
void dfs(int v) {
  used[v] = true;
  s[v] = d[v] > 0;
  for (int i = 0; i < (int)(g[v].size()); ++i) {
    int to = g[v][i].first;
    if (used[to]) {
      continue;
    }
    dfs(to);
    s[v] += s[to];
    if (s[to] % 2) {
      ans[g[v][i].second]++;
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  bool was = false;
  int sum = 0;
  for (int i = 0; i < (int)(n); ++i) {
    cin >> d[i];
    if (d[i] == -1) {
      was = true;
    }
    sum += d[i] > 0;
  }
  if (!was && sum % 2) {
    cout << -1 << endl;
    return 0;
  }
  if (sum % 2) {
    for (int i = 0; i < (int)(n); ++i) {
      if (d[i] == -1) {
        d[i] = 1;
        break;
      }
    }
  }
  for (int i = 0; i < (int)(m); ++i) {
    int a, b;
    cin >> a >> b;
    --a;
    --b;
    g[a].push_back(make_pair(b, i));
    g[b].push_back(make_pair(a, i));
  }
  dfs(0);
  int res = 0;
  for (int i = 0; i < (int)(m); ++i) {
    if (ans[i] % 2) {
      res++;
    }
  }
  cout << res << endl;
  for (int i = 0; i < (int)(m); ++i) {
    if (ans[i] % 2) {
      cout << i + 1 << endl;
    }
  }
  return 0;
}
