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 n, m;
int d[300010];
vector<pair<int, int> > G[300010];
bool f[300010];
vector<int> all;
int s;
int pos;
bool vis[300010];
int dep[300010];
int up[300010];
int par[300010];
void work(int x, int y) {
  if (dep[x] < dep[y]) swap(x, y);
  while (dep[x] > dep[y]) f[up[x]] = true, x = par[x];
  while (x != y) {
    f[up[x]] = true;
    f[up[y]] = true;
    x = par[x];
    y = par[y];
  }
}
int solve(int x) {
  vis[x] = true;
  vector<int> all;
  for (int i = 0; i < G[x].size(); i++) {
    int y = G[x][i].first;
    if (vis[y]) continue;
    up[y] = G[x][i].second;
    par[y] = x;
    dep[y] = dep[x] + 1;
    int t = solve(y);
    if (t) all.push_back(t);
  }
  if (d[x] == 1) all.push_back(x);
  for (int i = 0; i + 1 < all.size(); i += 2) work(all[i], all[i + 1]);
  if ((int)all.size() & 1)
    return all[(int)all.size() - 1];
  else
    return 0;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) {
    scanf("%d", d + i);
    s += (d[i] == 1);
    if (d[i] == -1) pos = i;
  }
  if (s & 1) {
    if (!pos) return !printf("-1");
    d[pos] = 1;
  }
  for (int i = 1; i <= m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    G[u].push_back(make_pair(v, i));
    G[v].push_back(make_pair(u, i));
  }
  solve(1);
  int ans = 0;
  for (int i = 1; i <= m; i++)
    if (f[i]) ans++;
  printf("%d\n", ans);
  for (int i = 1; i <= m; i++)
    if (f[i]) printf("%d\n", i);
  return 0;
}
