#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 10;
struct edge_t {
  int u, v;
  bool remains;
};
int get_other(int v, edge_t e) {
  if (e.v == v) return e.u;
  return e.v;
}
int arr[maxn];
vector<int> G[maxn];
edge_t edges[maxn];
bool vis[maxn];
void dfs(int v, int pareidx) {
  if (vis[v]) return;
  vis[v] = true;
  int down = 0;
  for (int eidx : G[v]) {
    int u = get_other(v, edges[eidx]);
    dfs(u, eidx);
    down += edges[eidx].remains;
  }
  if (arr[v] == -1) return;
  if (down % 2 != arr[v]) edges[pareidx].remains = true;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> arr[i];
  for (int i = 1; i <= m; i++) {
    int x, y;
    cin >> x >> y;
    edges[i].u = x;
    edges[i].v = y;
    edges[i].remains = false;
    G[x].push_back(i);
    G[y].push_back(i);
  }
  int midx = -1;
  int ones = 0;
  for (int i = 1; i <= n; i++) {
    if (arr[i] == -1)
      midx = i;
    else if (arr[i] == 1)
      ones++;
  }
  if (midx == -1 and (ones % 2) == 1) {
    cout << -1 << endl;
    return 0;
  }
  if (midx == -1)
    dfs(1, 0);
  else
    dfs(midx, 0);
  int ecnt = 0;
  for (int i = 1; i <= m; i++)
    if (edges[i].remains) ecnt++;
  cout << ecnt << endl;
  for (int i = 1; i <= m; i++)
    if (edges[i].remains) cout << i << endl;
  return 0;
}
