3 2
1 0 1
1 2
2 3
 10 10
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
6 7
8 3
6 4
4 2
9 2
5 10
9 8
10 7
5 1
6 2

2
1
2
 0

#include <bits/stdc++.h>
using namespace std;
struct edge {
  int r, nxt, w;
} e[300100 << 1];
int n, m, d[300100], sz[300100], head[300100], esz, tg[300100], vis[300100];
map<pair<int, int>, int> st;
int dfs(int u, int f) {
  if (f != -1)
    sz[u] = 1;
  else
    sz[u] = 0;
  vis[u] = 1;
  for (int s, t = head[u]; t; t = e[t].nxt)
    if (!vis[e[t].r]) s = dfs(e[t].r, u), sz[u] += s, (s ? tg[e[t].w] = 1 : 0);
  if (d[u] != -1 && sz[u] % 2 != d[u]) return 0;
  return 1;
}
void addedge(int u, int v, int w) {
  e[++esz].r = v;
  e[esz].nxt = head[u];
  head[u] = esz;
  e[esz].w = w;
  e[++esz].r = u;
  e[esz].nxt = head[v];
  head[v] = esz;
  e[esz].w = w;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) scanf("%d", &d[i]);
  for (int i = 1, u, v; i <= m; ++i)
    scanf("%d%d", &u, &v), st[pair<int, int>(u, v)] = i;
  for (auto s : st) addedge(s.first.first, s.first.second, s.second);
  int pos = 1, ans = 0;
  for (int i = 1; i <= n; ++i)
    if (d[i] == -1) pos = i;
  dfs(pos, -1);
  if (d[pos] != -1 && sz[pos] % 2 != d[pos]) return puts("-1"), 0;
  for (int i = 1; i <= m; ++i) ans += tg[i];
  printf("%d\n", ans);
  for (int i = 1; i <= m; ++i)
    if (tg[i]) printf("%d\n", i);
}
