#include <bits/stdc++.h>
using namespace std;
vector<int> v[300010];
vector<int> v2[300010];
int dap[300010], p, n, a[300010], m, x, y, ch[300010], sum;
void dfs(int x, int par, int pos) {
  int i;
  ch[x] = 1;
  for (i = 0; i < v[x].size(); i++) {
    if (ch[v[x][i]]) continue;
    dfs(v[x][i], x, v2[x][i]);
  }
  if (a[x] == -1 || a[x] == 0) return;
  if (a[x] == 1) {
    dap[pos] = 1;
    if (a[par] != -1) a[par] = (a[par] + 1) % 2;
  }
}
int main() {
  int i, cnt = 0;
  scanf("%d %d", &n, &m);
  for (i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    if (a[i] == -1) p = i;
    sum += a[i];
  }
  for (i = 1; i <= m; i++) {
    scanf("%d %d", &x, &y);
    v[x].push_back(y);
    v[y].push_back(x);
    v2[x].push_back(i);
    v2[y].push_back(i);
  }
  if (p)
    dfs(p, 0, 0);
  else {
    if (sum % 2 == 0)
      dfs(1, 0, 0);
    else {
      printf("-1");
      return 0;
    }
  }
  for (i = 1; i <= m; i++) {
    if (dap[i] == 1) cnt++;
  }
  printf("%d\n", cnt);
  for (i = 1; i <= m; i++) {
    if (dap[i] == 1) printf("%d\n", i);
  }
  return 0;
}
