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;
int n, m, i, cnt, mn, x, y, a[300300], b[300300];
vector<int> g[300300], f[300300], r;
bool u[300300];
void dfs(int i) {
  u[i] = true;
  if (a[i] == 1) b[i] = 1;
  for (int j = 0; j < g[i].size(); j++) {
    int k = g[i][j];
    if (u[k]) continue;
    dfs(k);
    b[i] += b[k];
    if (b[k] & 1) r.push_back(f[i][j]);
  }
}
int main() {
  scanf("%d%d", &n, &m);
  for (i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    if (a[i] == 1) cnt++;
    if (a[i] == -1) mn = i;
  }
  if (cnt & 1) {
    if (mn == 0) {
      puts("-1");
      return 0;
    }
    a[mn] = 1;
  }
  for (i = 1; i <= m; i++) {
    scanf("%d%d", &x, &y);
    g[x].push_back(y);
    f[x].push_back(i);
    g[y].push_back(x);
    f[y].push_back(i);
  }
  dfs(1);
  printf("%d\n", int(r.size()));
  for (i = 0; i < r.size(); i++) printf("%d\n", r[i]);
  return 0;
}
