#include <bits/stdc++.h>
using namespace std;
const int N = 3000 * 100 + 5;
vector<pair<int, int> > adj[N];
pair<int, int> edge[N];
short d[N];
bool mark[N], edg[N], c[N];
int bad[N], par[N], m, n;
void findd(int a, int e, int b) {
  while (a != b) {
    edg[e] = 1;
    if (a == edge[e].first)
      a = edge[e].second;
    else
      a = edge[e].first;
    e = par[a];
  }
  return;
}
void DFS2(int v, int parr) {
  mark[v] = 1;
  par[v] = parr;
  int s = adj[v].size();
  int temp = -1, temp2 = 0;
  if (c[v]) temp = v;
  for (int i = 0; i < s; i++) {
    int u = adj[v][i].first;
    int w = adj[v][i].second;
    if (!mark[u]) {
      DFS2(u, w);
      if (bad[u] != -1) {
        if (temp == -1) {
          temp = bad[u];
          temp2 = par[bad[u]];
        } else {
          findd(temp, temp2, v);
          findd(bad[u], par[bad[u]], v);
          temp = -1;
        }
      }
    }
  }
  bad[v] = temp;
  return;
}
void DFS(int v) {
  mark[v] = 1;
  int s = adj[v].size();
  for (int i = 0; i < s; i++) {
    int u = adj[v][i].first;
    int w = adj[v][i].second;
    if (!mark[u]) {
      DFS(u);
      if (c[u]) {
        c[v] = 1 - c[v];
        edg[w] = 1;
      }
    }
  }
  return;
}
void pp() {
  int t = 0;
  for (int i = 0; i < m; i++) {
    if (!edg[i]) t++;
  }
  printf("%d\n", t);
  for (int i = 0; i < m; i++) {
    if (!edg[i]) printf("%d\n", i + 1);
  }
  return;
}
int main() {
  int t = -1, x, y, k = 0;
  scanf("%d %d", &n, &m);
  for (int i = 0; i < n; i++) {
    scanf("%d", &d[i]);
    if (d[i] == -1) t = i;
  }
  for (int i = 0; i < m; i++) {
    scanf("%d %d", &x, &y);
    adj[--x].push_back(make_pair(--y, i));
    adj[y].push_back(make_pair(x, i));
    edge[i] = make_pair(x, y);
  }
  for (int i = 0; i < n; i++) {
    int s = adj[i].size();
    if (d[i] == 0 && s % 2) {
      k++;
      c[i] = 1;
    }
    if (d[i] == 1 && s % 2 == 0) {
      k++;
      c[i] = 1;
    }
  }
  if (t != -1) {
    DFS(t);
    pp();
  } else {
    t = 0;
    if (k % 2 == 1) {
      cout << "-1";
      return 0;
    }
    DFS2(0, m);
    pp();
  }
}
