#include <bits/stdc++.h>
using namespace std;
mt19937_64 rng((unsigned long long)new char);
const double eps = 1e-5;
const int maxn = 3e5 + 10;
const long long INF = 1e18;
const int mod = 998244353;
int n, m;
int d[maxn];
struct no {
  int u, v, id;
};
vector<no> edge, se;
vector<int> ans;
int pa[maxn];
vector<pair<int, int>> g[maxn];
int find(int x) { return x == pa[x] ? x : pa[x] = find(pa[x]); }
int fa[maxn];
int dep[maxn];
stack<int> ss;
int id[maxn];
void dfs(int u, int f, int d) {
  dep[u] = d;
  ss.push(u);
  for (auto r : g[u]) {
    if (r.first == f) continue;
    id[r.first] = r.second;
    fa[r.first] = u;
    dfs(r.first, u, d + 1);
  }
}
int cur[maxn];
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  bool hn = 0;
  bool cs = 0;
  for (int t = (0); t < (n); ++t) {
    cin >> d[t];
    if (d[t] == -1)
      hn = 1;
    else
      cs ^= d[t];
  }
  if (!hn && cs) {
    cout << -1;
    return 0;
  }
  if (cs) {
    bool fi = 0;
    for (int t = (0); t < (n); ++t) {
      if (d[t] == -1 && !fi) {
        fi = 1;
        d[t] = 1;
      } else if (d[t] == -1)
        d[t] = 0;
    }
  } else if (hn) {
    for (int t = (0); t < (n); ++t)
      if (d[t] == -1) d[t] = 0;
  }
  for (int t = (0); t < (m); ++t) {
    int u, v;
    cin >> u >> v;
    --u, --v;
    edge.push_back({u, v, t});
  }
  for (int t = (0); t < (n); ++t) pa[t] = t;
  int cnt = 0;
  for (int t = (0); t < (m); ++t) {
    int &u = edge[t].u, &v = edge[t].v;
    int fu = find(u), fv = find(v);
    if (fu != fv) {
      pa[fu] = fv;
      se.push_back(edge[t]);
      g[u].push_back({v, t}), g[v].push_back({u, t});
      if (++cnt == n - 1) break;
    }
  }
  dfs(0, -1, 0);
  while (!ss.empty()) {
    int c = ss.top();
    ss.pop();
    if (cur[c] != d[c]) ans.push_back(id[c] + 1), cur[fa[c]] ^= 1;
  }
  cout << ans.size() << "\n";
  for (auto r : ans) cout << r << "\n";
}
