#include <bits/stdc++.h>
using namespace std;
struct edge {
  int v, id;
};
vector<edge> g[300005];
const int maxn = 300005;
int par[maxn], a[maxn];
int find(int x) { return x == par[x] ? x : par[x] = find(par[x]); }
int sz[maxn];
vector<int> v;
void dfs(int u, int fa) {
  if (a[u]) sz[u] = 1;
  for (edge e : g[u]) {
    if (e.v == fa) continue;
    dfs(e.v, u);
    sz[u] += sz[e.v];
    if (sz[e.v] & 1) v.push_back(e.id);
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int i = 1; i <= n; ++i) par[i] = i;
  for (int i = 1; i <= m; ++i) {
    int u, v;
    cin >> u >> v;
    int x = find(u), y = find(v);
    if (x == y) continue;
    par[x] = y;
    g[u].push_back({v, i});
    g[v].push_back({u, i});
  }
  int rt = -1;
  for (int i = 1; i <= n; ++i)
    if (a[i] == -1) {
      rt = i;
      break;
    }
  if (rt != -1) {
    dfs(rt, -1);
  } else {
    int cnt = 0;
    for (int i = 1; i <= n; ++i)
      if (a[i] == 1) ++cnt;
    if (cnt & 1) return cout << -1 << '\n', 0;
    int rt = -1;
    for (int i = 1; i <= n; ++i)
      if (a[i] == 1) {
        rt = i;
        break;
      }
    if (rt == -1) return cout << 0 << '\n', 0;
    dfs(rt, -1);
  }
  cout << v.size() << '\n';
  for (int i : v) cout << i << '\n';
}
