#include <bits/stdc++.h>
using namespace std;
void getint(int &v) {
  char ch, fu = 0;
  for (ch = '*'; (ch < '0' || ch > '9') && ch != '-'; ch = getchar())
    ;
  if (ch == '-') fu = 1, ch = getchar();
  for (v = 0; ch >= '0' && ch <= '9'; ch = getchar()) v = v * 10 + ch - '0';
  if (fu) v = -v;
}
vector<pair<int, int> > a[300010];
vector<int> q, ANS;
int fa[300010], FA[300010], n, x, y, m, ans[300010], tag[300010], d[300010], s;
bool v[300010];
void dfs(int x, int l) {
  v[x] = 1;
  for (int i = 0; i < a[x].size(); ++i) {
    pair<int, int> y = a[x][i];
    if (y.first == l || v[y.first]) continue;
    fa[y.first] = x;
    FA[y.first] = y.second;
    dfs(y.first, x);
  }
}
void DFS(int x, int l) {
  v[x] = 1;
  for (int i = 0; i < a[x].size(); ++i) {
    pair<int, int> y = a[x][i];
    if (y.first == l || v[y.first]) continue;
    DFS(y.first, x);
    tag[x] += tag[y.first];
  }
  ans[FA[x]] = tag[x] % 2;
}
int main() {
  scanf("%d%d", &n, &m);
  for (long long i = 1; i <= n; i++) {
    getint(d[i]);
    if (d[i]) {
      ++s;
      q.push_back(i);
    }
  }
  for (long long i = 1; i <= m; i++) {
    getint(x), getint(y);
    a[x].push_back(make_pair(y, i));
    a[y].push_back(make_pair(x, i));
  }
  dfs(1, 0);
  memset(v, 0, sizeof(v));
  if (s % 2 == 1) {
    int x = 0;
    for (long long i = 1; i <= n; i++)
      if (d[i] == -1) {
        x = i;
        break;
      }
    if (!x) return puts("-1"), 0;
    ++s;
    q.push_back(x);
  }
  for (long long i = 0; i <= s - 1; i++) tag[q[i]] ^= 1;
  DFS(1, 0);
  for (long long i = 1; i <= m; i++)
    if (ans[i]) ANS.push_back(i);
  cout << ANS.size() << endl;
  for (int i = 0; i < ANS.size(); ++i) printf("%d\n", ANS[i]);
  return 0;
}
