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 N = 3e5 + 7, M = 2 * N;
int edge[M], succ[M], ver[N], idx, ID[M];
int d[N], all, have, fa[N], vis[N];
vector<int> ans;
void add(int u, int v, int id) {
  edge[idx] = v;
  succ[idx] = ver[u];
  ID[idx] = id;
  ver[u] = idx++;
}
void dfs1(int u) {
  vis[u] = 1;
  if (d[u] == -1)
    have = u;
  else if (d[u] == 1)
    ++all;
  for (int i = ver[u]; ~i; i = succ[i]) {
    int v = edge[i];
    if (vis[v]) continue;
    fa[v] = u;
    dfs1(v);
  }
}
void dfs2(int u) {
  for (int i = ver[u]; ~i; i = succ[i]) {
    int v = edge[i];
    if (fa[v] == u) {
      dfs2(v);
      if (d[v] == 1) ans.push_back(ID[i]), d[u] ^= 1;
    }
  }
}
int main() {
  memset(ver, -1, sizeof ver);
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%d", &d[i]);
  set<pair<int, int> > st;
  for (int i = 1; i <= m; ++i) {
    int u, v;
    scanf("%d%d", &u, &v);
    if (u > v) swap(u, v);
    if (st.count({u, v})) continue;
    st.insert({u, v});
    add(u, v, i), add(v, u, i);
  }
  dfs1(1);
  if (all & 1) {
    if (!have) return puts("-1"), 0;
    d[have] = 1;
  }
  for (int i = 1; i <= n; ++i)
    if (d[i] == -1) d[i] = 0;
  dfs2(1);
  printf("%d\n", (int)ans.size());
  for (auto& v : ans) printf("%d\n", v);
  return 0;
}
