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;
vector<int> g[300300];
vector<pair<int, int> > e;
int c[300300], st[300300];
set<pair<int, int> > forb;
void dfs(int v, int p) {
  st[v] = 1;
  for (auto to : g[v]) {
    if (!st[to]) dfs(to, v);
  }
  if (c[v]) {
    forb.insert({v, p});
    forb.insert({p, v});
    c[v] = 0;
    c[p] ^= 1;
  }
}
void solve() {
  int n, m, ones = 0, minus = 0;
  scanf("%d %d", &n, &m);
  for (int i = 0; i < n; ++i) {
    scanf("%d", &c[i]);
    if (c[i] == 1) ones ^= 1;
    if (c[i] == -1) minus = 1;
  }
  if (ones && !minus) {
    puts("-1");
    return;
  }
  if (ones) {
    for (int i = 0; i < n; ++i) {
      if (c[i] == -1) {
        if (minus)
          c[i] = 1, minus = 0;
        else
          c[i] = 0;
      }
    }
  }
  for (int i = 0; i < m; ++i) {
    int a, b;
    scanf("%d%d", &a, &b);
    --a;
    --b;
    e.push_back({a, b});
    g[a].push_back(b);
    g[b].push_back(a);
  }
  for (int i = 0; i < n; ++i) c[i] ^= (g[i].size() % 2);
  dfs(0, -1);
  vector<int> ans;
  for (int i = 0; i < m; ++i) {
    if (forb.find(e[i]) == forb.end()) {
      ans.push_back(i + 1);
    } else {
      forb.erase(e[i]);
      forb.erase({e[i].second, e[i].first});
    }
  }
  printf("%d\n", ans.size());
  for (int i = 0; i < ans.size(); ++i) {
    printf("%d ", ans[i]);
  }
}
int main() {
  solve();
  return 0;
}
