#include <bits/stdc++.h>
using namespace std;
const int Nmax = 3e5 + 5;
struct edge {
  int v, id;
};
vector<edge> adj[Nmax];
vector<int> ans;
int c[Nmax];
int n, m, u, v, top;
bool flag[Nmax];
bool visited[Nmax];
bool ok;
int dfs(int u, int up) {
  visited[u] = true;
  int sum = 0;
  for (auto [v, id] : adj[u]) {
    if (visited[v]) continue;
    sum += dfs(v, id);
  }
  if ((adj[u].size() - sum) % 2 != c[u]) {
    flag[up] = true;
    return 1;
  }
  return 0;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    cin >> c[i];
  }
  for (int i = 1; i <= m; i++) {
    cin >> u >> v;
    adj[u].push_back({v, i});
    adj[v].push_back({u, i});
  }
  int one = 0;
  int pos = 0;
  for (int i = 1; i <= n; i++) {
    cin >> c[i];
    if (c[i] == 1) one++;
    if (c[i] == -1) pos = i;
  }
  if (pos == 0 && one % 2 == 1) return cout << -1, 0;
  if (one % 2) c[pos] = 1;
  for (int i = 1; i <= n; i++) {
    if (c[i] == -1) c[i]++;
  }
  int x = dfs(1, -1);
  for (int i = 1; i <= m; i++) {
    if (!flag[i]) ans.push_back(i);
  }
  cout << ans.size() << "\n";
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i] << "\n";
  }
  return 0;
}
