#include <bits/stdc++.h>
using namespace std;
struct edge {
  int a, b, used;
};
const int mx = 1000000;
int n, m, deg[mx], base_v[mx], deg1[mx];
vector<edge> e;
vector<int> g[mx];
vector<vector<int> > cmp;
bool used[mx];
void add_edge(int u, int v) {
  g[u].push_back(e.size());
  g[v].push_back(e.size() + 1);
  e.push_back({u, v, 0});
  e.push_back({v, u, 0});
}
void cmp_dfs(int v) {
  used[v] = 1;
  cmp.back().push_back(v);
  for (auto id : g[v]) {
    int to = e[id].b;
    if (!used[to]) cmp_dfs(to);
  }
}
void color(int v, int en, int pv) {
  used[v] = 1;
  for (auto id : g[v]) {
    int to = e[id].b;
    if (!used[to]) color(to, id, v);
  }
  if (deg1[v] % 2 != deg[v] && en > -1) {
    e[en].used = 1;
    e[en ^ 1].used = 1;
    deg1[v]++;
    deg1[pv]++;
  }
}
int main() {
  cin >> n >> m;
  int u, v;
  for (int i = 0; i < n; ++i) {
    cin >> deg[i];
    base_v[i] = -1;
    used[i] = 0;
    deg1[i] = 0;
  }
  for (int i = 0; i < m; ++i) {
    cin >> u >> v;
    add_edge(u - 1, v - 1);
  }
  for (int i = 0; i < n; ++i) {
    if (!used[i]) {
      cmp.push_back(vector<int>());
      cmp_dfs(i);
    }
  }
  int cn = cmp.size();
  for (int i = 0; i < cn; ++i) {
    int sum = 0;
    for (auto v : cmp[i]) {
      if (deg[v] == -1) {
        sum = 0;
        base_v[i] = v;
        break;
      } else
        sum += deg[v];
    }
    if (sum % 2 == 1) {
      cout << -1 << endl;
      return 0;
    }
  }
  for (int i = 0; i < n; ++i) {
    used[i] = 0;
    if (deg[i] == -1) deg[i] = 0;
  }
  for (int i = 0; i < cn; ++i) {
    if (base_v[i] == -1)
      color(cmp[i][0], -1, -1);
    else
      color(base_v[i], -1, -1);
  }
  int k = 0;
  for (int i = 0; i < m; ++i) {
    if (e[i * 2].used == 1) k++;
  }
  cout << k << endl;
  for (int i = 0; i < m; ++i) {
    if (e[i * 2].used == 1) cout << i + 1 << " ";
  }
  cout << endl;
  return 0;
}
