#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9 + 7;
const int N = 3e5 + 10;
vector<pair<int, int>> vp[N];
vector<int> v[N];
int pos[N];
int deg[N];
int vis[N];
vector<int> ans;
void dfs(int x, int p = 0, int o = 0) {
  if (vis[x]) return;
  v[p].push_back(x);
  vis[x] = 1;
  pos[x] = o;
  for (auto &pp : vp[x]) {
    int y, oo;
    tie(y, oo) = pp;
    dfs(y, x, oo);
  }
}
int solve(int x) {
  int cur = deg[x];
  for (auto &y : v[x]) {
    cur ^= solve(y);
  }
  if (cur) ans.push_back(pos[x]);
  return cur;
}
int main() {
  int n, m;
  cin >> n >> m;
  int cnt1 = 0, cnt_1 = 0;
  for (int i = 1; i <= n; i++) {
    cin >> deg[i];
    if (deg[i] == 1) cnt1 ^= 1;
    if (deg[i] == -1) cnt_1++;
  }
  if (cnt1 == 1 && cnt_1 == 0) {
    puts("-1");
    return 0;
  }
  for (int i = 1; i <= n; i++) {
    if (deg[i] == -1) {
      deg[i] = cnt1;
      cnt1 = 0;
    }
  }
  for (int i = 1; i <= m; i++) {
    int x, y;
    cin >> x >> y;
    vp[x].push_back({y, i});
    vp[y].push_back({x, i});
  }
  dfs(1);
  solve(1);
  printf("%d\n", ans.size());
  for (auto &x : ans) printf("%d\n", x);
  return 0;
}
