3 2
1 0 1
1 2
2 3
 10 10
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
6 7
8 3
6 4
4 2
9 2
5 10
9 8
10 7
5 1
6 2

2
1
2
 0

#include <bits/stdc++.h>
using namespace std;
int d[300010], deg[300010] = {0};
pair<int, int> par[300010];
bool vis[300010] = {0}, pres[300010] = {0};
vector<pair<int, int> > adj[300010];
vector<pair<int, pair<int, int> > > ans;
int dfs(int v, int p) {
  int ret = -1;
  vis[v] = true;
  for (int i = 0; i < adj[v].size(); ++i) {
    int t = adj[v][i].first, id = adj[v][i].second;
    if (vis[t]) continue;
    par[t] = make_pair(v, id);
    int r = dfs(t, v);
    if (r == -1) continue;
    if (ret == -1)
      ret = r;
    else {
      ans.push_back(make_pair(v, make_pair(ret, r)));
      ret = -1;
    }
  }
  if (d[v] == 1 || d[v] == -1) {
    if (ret == -1 && d[v] == 1)
      ret = v;
    else if (ret != -1) {
      ans.push_back(make_pair(v, make_pair(ret, v)));
      ret = -1;
    }
  }
  return ret;
}
int main() {
  int n, m, r = -1;
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%d", d + i);
  for (int i = 1; i <= m; ++i) {
    int u, v;
    scanf("%d %d", &u, &v);
    ++deg[u];
    ++deg[v];
    adj[u].push_back(make_pair(v, i));
    adj[v].push_back(make_pair(u, i));
  }
  for (int i = 1; i <= n; ++i) {
    if (d[i] == -1) {
      r = i;
      continue;
    }
    if (deg[i] % 2 != d[i])
      d[i] = 1;
    else {
      if (r == -1) r = i;
      d[i] = 0;
    }
  }
  int ret = 0;
  if (r == -1) r = 1;
  ret = dfs(r, r);
  if (ret != -1) {
    printf("-1\n");
    return 0;
  }
  int cnt = 0;
  for (int i = 0; i < ans.size(); ++i) {
    int p = ans[i].first, v = ans[i].second.first, u = ans[i].second.second;
    while (v != p) {
      pres[par[v].second] = true;
      ++cnt;
      v = par[v].first;
    }
    while (u != p) {
      pres[par[u].second] = true;
      ++cnt;
      u = par[u].first;
    }
  }
  printf("%d\n", m - cnt);
  for (int i = 1; i <= m; ++i)
    if (!pres[i]) printf("%d ", i);
  printf("\n");
  return 0;
}
