#include <bits/stdc++.h>
using namespace std;
const int LIM_N = 3e5 + 5;
set<int> ans;
int pr[LIM_N];
vector<pair<int, int> > adj[LIM_N];
bool usd[LIM_N];
void dfs(const int pos = 0, const int pv = -1, const int pe = -1) {
  usd[pos] = true;
  for (const auto nxt : adj[pos]) {
    if (!usd[nxt.second]) dfs(nxt.second, pos, nxt.first);
  }
  if (pr[pos]) {
    pr[pv] ^= 1;
    ans.insert(pe);
  }
}
int main() {
  int N, E;
  int lastNeg = -1;
  int p = 0;
  scanf("%d%d", &N, &E);
  for (int i = 0; i < N; i++) {
    scanf("%d", &pr[i]);
    if (pr[i] == -1)
      lastNeg = i;
    else
      p ^= pr[i];
  }
  for (int i = 0, a, b; i < E; i++) {
    scanf("%d%d", &a, &b);
    a--, b--;
    adj[a].emplace_back(i, b);
    adj[b].emplace_back(i, a);
  }
  if (p && lastNeg == -1) {
    printf("-1\n");
    return 0;
  }
  if (p) pr[lastNeg] = 1;
  for (int i = 0; i < N; i++)
    if (pr[i] == -1) pr[i] = 0;
  dfs();
  printf("%d\n", (int)ans.size());
  for (const int a : ans) printf("%d\n", a + 1);
}
