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;
vector<int> g[300300];
int d[300300];
int x[300300], y[300300];
bool used[300300];
bool flag = false;
bool ok = true;
int sum;
vector<int> G[300300];
int D[300300];
void dfs1(int s) {
  if (d[s] == -1)
    flag = true;
  else
    sum += d[s];
  used[s] = true;
  for (int t : g[s]) {
    if (!used[t]) dfs1(t);
  }
}
void dfs2(int s, bool f) {
  if (d[s] == -1 and !f) {
    d[s] = 1;
    f = true;
  }
  used[s] = true;
  for (int t : g[s]) {
    if (!used[t]) dfs2(t, f);
  }
}
void dfs3(int s, int p) {
  if (p != -1) G[p].push_back(s);
  used[s] = true;
  for (int t : g[s]) {
    if (!used[t]) {
      dfs3(t, s);
    }
  }
}
set<pair<int, int>> edge;
void dfs4(int s, int p) {
  D[s] = d[s];
  for (int t : G[s]) {
    dfs4(t, s);
    if (D[s] == 0) {
      if (D[t] == 1) {
        edge.insert(make_pair(s, t));
        edge.insert(make_pair(t, s));
        D[s] ^= 1;
      }
    } else if (D[s] == 1) {
      if (D[t] == 1) {
        edge.insert(make_pair(s, t));
        edge.insert(make_pair(t, s));
        D[s] ^= 1;
      }
    }
  }
}
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  for (int i = 0; i < n; i++) {
    cin >> d[i];
  }
  for (int i = 0; i < m; i++) {
    cin >> x[i] >> y[i];
    x[i]--;
    y[i]--;
    g[x[i]].push_back(y[i]);
    g[y[i]].push_back(x[i]);
  }
  set<int> odd;
  for (int i = 0; i < n; i++) {
    if (!used[i]) {
      flag = false;
      sum = 0;
      dfs1(i);
      if (!flag and sum % 2) {
        printf("-1\n");
        return 0;
      } else if (sum % 2)
        odd.insert(i);
    }
  }
  for (int i = 0; i < n; i++) {
    used[i] = 0;
  }
  for (int i = 0; i < n; i++) {
    if (!used[i] and odd.find(i) != odd.end()) {
      dfs2(i, false);
    }
  }
  for (int i = 0; i < n; i++) {
    if (d[i] == -1) d[i] = 0;
    used[i] = false;
  }
  for (int i = 0; i < n; i++) {
    if (!used[i]) {
      dfs3(i, -1);
      dfs4(i, -1);
    }
  }
  vector<int> res;
  for (int i = 0; i < m; i++) {
    if (edge.find(make_pair(x[i], y[i])) != edge.end()) {
      edge.erase(make_pair(x[i], y[i]));
      edge.erase(make_pair(y[i], x[i]));
    } else
      res.push_back(i + 1);
  }
  printf("%d\n", res.size());
  for (int r : res) {
    printf("%d\n", r);
  }
}
