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;
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
int visv[300007], ans[300007], us[300007], n, m, d[300007];
vector<pair<int, int> > edge[300007];
int dfs(int nd) {
  int ret = 0;
  for (int k = 0; k < edge[nd].size(); k++) {
    int v = edge[nd][k].first;
    if (visv[v]) continue;
    visv[v] = 1;
    int p = dfs(v);
    int e = edge[nd][k].second;
    if (p) ans[e] = 1;
    ret += p;
    us[nd] |= us[v];
  }
  ret %= 2;
  if (d[nd] == -1 || ret == d[nd]) return 0;
  return 1;
}
void dfs2(int nd) {
  if (d[nd] == -1) return;
  for (int k = 0; k < edge[nd].size(); k++) {
    int v = edge[nd][k].first;
    if (visv[v]) continue;
    visv[v] = 1;
    if (us[v] == 0) continue;
    dfs2(v);
    ans[edge[nd][k].second] ^= 1;
    return;
  }
}
int main() {
  int i, u, v;
  scanf("%d %d", &n, &m);
  for (i = 1; i <= n; i++) {
    scanf("%d", &d[i]);
    us[i] = (d[i] == -1);
    ;
  }
  for (i = 1; i <= m; i++) {
    scanf("%d %d", &u, &v);
    edge[u].push_back({v, i});
    edge[v].push_back({u, i});
  }
  visv[1] = 1;
  int p = dfs(1);
  memset(visv, 0, sizeof visv);
  visv[1] = 1;
  if (p) {
    if (!us[1])
      return printf("-1\n") & 0;
    else
      dfs2(1);
  }
  int tot = 0;
  for (i = 1; i <= m; i++) tot += ans[i];
  printf("%d\n", tot);
  for (i = 1; i <= m; i++)
    if (ans[i]) printf("%d\n", i);
  return 0;
}
