#include <bits/stdc++.h>
using namespace std;
int par[300005], ran[300005];
void init() {
  for (int i = 0; i < 300005; i++) par[i] = i;
}
int find(int x) {
  if (x == par[x])
    return x;
  else
    return par[x] = find(par[x]);
}
void unite(int x, int y) {
  x = find(x);
  y = find(y);
  if (x == y) return;
  if (ran[x] < ran[y])
    par[x] = y;
  else {
    par[y] = x;
    if (ran[x] == ran[y]) ran[x]++;
  }
}
bool same(int x, int y) { return find(x) == find(y); }
int n, m, p[300005];
vector<int> edge[300005];
int lca[300005][21], dep[300005];
void dfs(int v, int u) {
  lca[v][0] = u;
  if (u == -1)
    dep[v] = 0;
  else
    dep[v] = dep[u] + 1;
  for (int i = 0; i < edge[v].size(); i++) {
    if (edge[v][i] == u) continue;
    dfs(edge[v][i], v);
  }
}
int cnt[300005];
vector<pair<int, int> > ans;
int dfs2(int v, int u) {
  int a = cnt[v];
  for (int i = 0; i < edge[v].size(); i++) {
    if (edge[v][i] == u) continue;
    int f = dfs2(edge[v][i], v);
    a += f;
    if (f % 2 == 1) ans.push_back(make_pair(edge[v][i], v));
  }
  return a;
}
int main() {
  cin >> n >> m;
  int a = 0, b = 0;
  for (int i = 1; i <= n; i++) {
    scanf("%d", &p[i]);
    if (p[i] == 1)
      a++;
    else if (p[i] == -1)
      b = i;
  }
  if (a % 2 == 1 && b == 0) {
    puts("-1");
    return 0;
  } else if (a % 2 == 1)
    p[b] = 1;
  init();
  map<pair<int, int>, int> M;
  for (int i = 0; i < m; i++) {
    int a, b;
    scanf("%d%d", &a, &b);
    if (!same(a, b) && a != b && M.find(make_pair(a, b)) == M.end() &&
        M.find(make_pair(b, a)) == M.end()) {
      M[make_pair(a, b)] = i + 1;
      M[make_pair(b, a)] = i + 1;
      unite(a, b);
      edge[a].push_back(b);
      edge[b].push_back(a);
    }
  }
  vector<int> vec;
  for (int i = 1; i <= n; i++)
    if (p[i] == 1) vec.push_back(i);
  dfs(1, -1);
  for (int j = 0; j < 20; j++) {
    for (int i = 1; i <= n; i++) {
      if (lca[i][j] == -1)
        lca[i][j + 1] = -1;
      else
        lca[i][j + 1] = lca[lca[i][j]][j];
    }
  }
  for (int i = 0; i < vec.size(); i += 2) {
    int a = vec[i], b = vec[i + 1];
    cnt[a]++;
    cnt[b]++;
    if (dep[a] > dep[b]) swap(a, b);
    for (int j = 20; j >= 0; j--) {
      if (!(((dep[b] - dep[a]) >> j) & 1)) continue;
      b = lca[b][j];
    }
    for (int j = 20; j >= 0; j--) {
      if (lca[a][j] != lca[b][j]) {
        a = lca[a][j];
        b = lca[b][j];
      }
    }
  }
  dfs2(1, -1);
  cout << ans.size() << endl;
  for (int i = 0; i < ans.size(); i++) {
    if (M.find(ans[i]) != M.end())
      printf("%d\n", M[ans[i]]);
    else
      printf("%d\n", M[make_pair(ans[i].second, ans[i].first)]);
  }
}
