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;
void doRoutine() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
}
struct edge {
  int from, to, id;
  edge(int a = 0, int b = 0, int id = 0) : from(a), to(b), id(id) {}
};
const int MAXN = 300005;
int cur[MAXN], d[MAXN];
vector<int> ans;
bool used[MAXN];
void dfs(int v, edge bedge, vector<vector<edge> > &g) {
  used[v] = true;
  for (auto e : g[v]) {
    if (!used[e.to]) {
      dfs(e.to, e, g);
    }
  }
  if (d[v] != -1 && cur[v] != d[v]) {
    if (bedge.id == -1) {
      cout << -1;
      exit(0);
    }
    ans.push_back(bedge.id);
    ++cur[v];
    cur[v] %= 2;
    ++cur[bedge.from];
    cur[bedge.from] %= 2;
  }
}
signed main() {
  int n, m;
  cin >> n >> m;
  int start = 0;
  for (int i = 0; i < n; ++i) {
    cin >> d[i];
    if (d[i] == -1) {
      start = i;
    }
  }
  vector<vector<edge> > g(n);
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    --a;
    --b;
    g[a].push_back(edge(a, b, i + 1));
    g[b].push_back(edge(b, a, i + 1));
  }
  dfs(start, edge(-1, -1, -1), g);
  cout << ans.size() << endl;
  for (auto x : ans) {
    cout << x << endl;
  }
  return 0;
}
