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>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
template <class T, class U>
inline void Max(T &a, U b) {
  if (a < b) a = b;
}
template <class T, class U>
inline void Min(T &a, U b) {
  if (a > b) a = b;
}
inline void add(int &a, int b) {
  a += b;
  while (a >= 1000000007) a -= 1000000007;
}
int pow(int a, int b) {
  int ans = 1;
  while (b) {
    if (b & 1) ans = ans * (long long)a % 1000000007;
    a = (long long)a * a % 1000000007;
    b >>= 1;
  }
  return ans;
}
int pow(int a, int b, int c) {
  long long ans = 1;
  while (b) {
    if (b & 1) ans = ans * a % c;
    a = 1LL * a * a % c;
    b >>= 1;
  }
  return ans;
}
int a[300010];
vector<pair<int, int> > g[300010];
int vis[300010];
vector<int> res;
int dfs(int u) {
  for (auto o : g[u]) {
    if (vis[o.second]) continue;
    res.push_back(o.second);
    vis[o.second] = 1;
    if (a[o.first]) {
      return 1;
    }
    if (dfs(o.second)) return 1;
    res.pop_back();
  }
  return 0;
}
int s[300010], top, id[300010];
int go(int u) {
  s[++top] = u, id[u] = top;
  for (auto o : g[u])
    if (a[o.first] == 0) {
      if (!vis[o.second]) {
        res.push_back(o.second);
        vis[o.second] = 1;
        if (id[o.first]) {
          vector<int> re;
          while (top != id[o.first]) {
            re.push_back(res.back());
            res.pop_back();
            top--;
          }
          res = re;
          return 1;
        } else if (go(o.first))
          return 1;
        res.pop_back();
      }
    }
  top--;
  return 0;
}
int main() {
  int j, k, i, T, ca = 0, n, m, K;
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; i++) scanf("%d", &a[i]);
  int ans = 0;
  for (int i = 0; i < m; i++) {
    scanf("%d%d", &j, &k);
    j--, k--;
    if (!ans && (a[j] && a[k])) {
      ans = i + 1;
    } else if (!ans) {
      g[j].push_back({k, i});
      g[k].push_back({j, i});
    }
  }
  if (ans) {
    printf("1\n%d\n", ans);
    return 0;
  }
  int ok = 1;
  for (int i = 0; i < n; i++)
    if (a[i] != -1 && (int)(g[i].size()) % 2 != a[i]) {
      ok = 0;
      break;
    }
  if (ok) {
    puts("0");
    return 0;
  }
  for (int i = 0; i < n; i++)
    if (a[i]) {
      res.clear();
      top = 0;
      if (dfs(i)) {
        sort(res.begin(), res.end());
        printf("%d\n", (int)(res.size()));
        for (auto first : res) printf("%d\n", first + 1);
        return 0;
      }
    }
  memset(vis, 0, sizeof(vis));
  for (int i = 0; i < n; i++)
    if (!a[i] && (int)(g[i].size()) > 1) {
      res.clear();
      top = 0;
      if (go(i)) {
        sort(res.begin(), res.end());
        for (auto first : res) printf("%d\n", first + 1);
        return 0;
      }
    }
  puts("-1");
  return 0;
}
