#include <bits/stdc++.h>
using namespace std;
const int max_n = 300333, inf = 1011111111;
int n, m, a[max_n], used[max_n], pos, lb[max_n];
vector<int> g2[max_n], num2[max_n], g[max_n], num[max_n], k, ans;
void dfs(int v) {
  used[v] = 1;
  for (int i = 0; i < g2[v].size(); ++i) {
    if (used[g2[v][i]] == 0) {
      g[v].push_back(g2[v][i]);
      num[v].push_back(num2[v][i]);
      dfs(g2[v][i]);
    }
  }
}
void dfs2(int v) {
  for (int i = 0; i < g[v].size(); ++i) {
    dfs2(g[v][i]);
    lb[v] ^= lb[g[v][i]];
    if (lb[g[v][i]]) {
      ans.push_back(num[v][i]);
    }
  }
}
int main() {
  scanf("%d%d", &n, &m);
  pos = -1;
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &a[i]);
    if (a[i] == -1) {
      pos = i;
    }
    if (a[i] == 1) {
      k.push_back(i);
    }
  }
  if (pos == -1 && k.size() % 2 != 0) {
    printf("-1\n");
    return 0;
  }
  for (int i = 0; i < m; ++i) {
    int u, v;
    scanf("%d%d", &u, &v);
    g2[u].push_back(v);
    g2[v].push_back(u);
    num2[u].push_back(i);
    num2[v].push_back(i);
  }
  dfs(1);
  for (int i = 0; i + 1 < k.size(); i += 2) {
    lb[k[i]] = 1;
    lb[k[i + 1]] = 1;
  }
  if (k.size() % 2) {
    lb[pos] = 1;
    lb[k.back()] = 1;
  }
  dfs2(1);
  printf("%d\n", ans.size());
  for (int i = 0; i < ans.size(); ++i) {
    printf("%d\n", ans[i] + 1);
  }
  return 0;
}
