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 V = 3 * (int)1e5 + 10;
const int E = 6 * (int)1e5 + 10;
int head[V], nxt[E], cur[E], idx[E];
int d[V], b[V], ne = 1;
bool vi[V];
vector<int> result;
void InitHead() {
  memset(head, 0, sizeof(head));
  memset(b, 0, sizeof(b));
}
void AddEdge(int u, int v, int c) {
  idx[ne] = c, cur[ne] = v;
  nxt[ne] = head[u], head[u] = ne++;
}
void dfs(int u) {
  if (d[u] == 1) b[u] = 1;
  vi[u] = true;
  for (int itor = head[u]; itor; itor = nxt[itor]) {
    int v = cur[itor];
    if (vi[v]) continue;
    dfs(v);
    b[u] += b[v];
    if (b[v] & 1) result.push_back(idx[itor]);
  }
}
int main() {
  int n, m, cnt1 = 0, agi = -1;
  InitHead();
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &d[i]);
    if (d[i] == 1) ++cnt1;
    if (d[i] == -1) agi = i;
  }
  if (cnt1 & 1) {
    if (agi == -1) {
      puts("-1");
      return 0;
    }
    d[agi] = 1;
  }
  for (int i = 0; i < m; ++i) {
    int u, v;
    scanf("%d %d", &u, &v);
    AddEdge(u, v, i + 1);
    AddEdge(v, u, i + 1);
  }
  dfs(1);
  printf("%d\n", (int)result.size());
  for (int i = 0; i < (int)result.size(); ++i) {
    printf("%d\n", result[i]);
  }
  return 0;
}
