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;
const int MAXN = 3e5 + 5;
int n, m;
int d[MAXN];
vector<int> graph[MAXN];
int degree[MAXN];
map<pair<int, int>, int> edgeIndex;
queue<int> q;
vector<int> startNodes;
vector<int> level[MAXN];
int dist[MAXN], parent[MAXN];
bool used[MAXN];
vector<int> answer;
void addEdge(int u, int v) {
  degree[u]++;
  degree[v]++;
  answer.push_back(edgeIndex[{u, v}]);
}
bool checkNode(int x) {
  if (d[x] == -1) return true;
  if (degree[x] % 2 == d[x]) return true;
  return false;
}
int BFS() {
  int maxLevel = 1;
  for (int x : startNodes) {
    q.push(x);
    dist[x] = 1;
  }
  while (q.empty() == false) {
    int x = q.front();
    q.pop();
    level[dist[x]].push_back(x);
    maxLevel = max(maxLevel, dist[x]);
    for (int y : graph[x]) {
      if (dist[y] == -1) {
        dist[y] = dist[x] + 1;
        parent[y] = x;
        q.push(y);
      }
    }
  }
  return maxLevel;
}
int cnt1 = 0;
void DFS(int x) {
  used[x] = true;
  if (d[x] == 1) cnt1++;
  if (d[x] == -1) startNodes.push_back(x);
  for (int y : graph[x]) {
    if (used[y] == false) {
      DFS(y);
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  memset(dist, -1, sizeof(dist));
  memset(parent, -1, sizeof(parent));
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    cin >> d[i];
  }
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    edgeIndex[{u, v}] = i + 1;
    edgeIndex[{v, u}] = i + 1;
    graph[u].push_back(v);
    graph[v].push_back(u);
  }
  for (int i = 1; i <= n; i++) {
    if (used[i] == false) {
      cnt1 = 0;
      startNodes.clear();
      DFS(i);
      if (cnt1 % 2 != 0 && startNodes.empty() == true) {
        cout << "-1" << '\n';
        exit(0);
      }
      if (startNodes.empty() == true) {
        startNodes = vector<int>{i};
      }
      int maxLevel = BFS();
      for (int lvl = maxLevel; lvl >= 1; lvl--) {
        for (int x : level[lvl]) {
          if (checkNode(x) == false) {
            addEdge(x, parent[x]);
          }
        }
        level[lvl].clear();
      }
    }
  }
  for (int i = 1; i <= n; i++) {
    if (checkNode(i) == false) {
      cout << "FAK " << i << '\n';
    }
  }
  cout << answer.size() << '\n';
  for (int i = 0; i < answer.size(); i++) {
    cout << answer[i] << " ";
  }
  cout << '\n';
}
