#include <bits/stdc++.h>
using namespace std;
const int sz = 3e5 + 10;
vector<pair<int, int> > sv[sz];
int n, m, va[sz], st[sz], si[sz], qq = 0;
bool us[sz], us2[sz];
void dfs(int v, int pr, int nu) {
  us2[v] = 1;
  for (int a = 0; a < sv[v].size(); a++) {
    int ne = sv[v][a].first, nenu = sv[v][a].second;
    if (us2[ne] == 0) dfs(ne, v, nenu);
  }
  if (va[v] != -1 and st[v] % 2 != va[v]) {
    us[nu] = 1, st[v]++, st[pr]++, qq++;
  }
}
void dfs2(int v, int nu) {
  us2[v] = 1;
  si[v] = va[v];
  for (int a = 0; a < sv[v].size(); a++) {
    int ne = sv[v][a].first, nenu = sv[v][a].second;
    if (us2[ne] == 0) {
      dfs2(ne, nenu);
      si[v] += si[ne];
    }
  }
  if (si[v] % 2 == 1) {
    us[nu] = 1, qq++;
  }
}
int main() {
  cin >> n >> m;
  int fo = -1, q1 = 0;
  for (int a = 0; a < n; a++) {
    scanf("%d", &va[a]);
    if (va[a] == -1) fo = a;
    if (va[a] == 1) q1++;
    st[a] = 0, us2[a] = 0;
  }
  for (int a = 0; a < m; a++) {
    int u, v;
    scanf("%d%d", &u, &v);
    u--, v--;
    sv[u].push_back(make_pair(v, a));
    sv[v].push_back(make_pair(u, a));
    us[a] = 0;
  }
  if (fo != -1) {
    dfs(fo, -1, -1);
    cout << qq << "\n";
    for (int a = 0; a < m; a++) {
      if (us[a]) printf("%d\n", a + 1);
    }
  } else {
    if (q1 % 2 == 1)
      cout << -1;
    else {
      dfs2(0, -1);
      cout << qq << "\n";
      for (int a = 0; a < m; a++) {
        if (us[a]) printf("%d\n", a + 1);
      }
    }
  }
}
