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 u, v, id;
  edge *next;
} pool[300005 << 1], *h[300005];
struct pa {
  int x, y, id;
  bool operator<(const pa &a) const {
    if (x != a.x) return x < a.x;
    return y < a.y;
  }
} eg[300005];
int cnt = 0;
void addedge(int u, int v, int id) {
  edge *new1 = &pool[cnt++];
  new1->u = u, new1->v = v, new1->id = id, new1->next = h[u], h[u] = new1;
}
int n, m;
int dp[2][300005];
int d[300005];
int dep[300005];
void dfs(int a, int fa) {
  dp[0][a] = dp[1][a] = 0;
  int lks = 0;
  for (edge *p = h[a]; p; p = p->next) {
    if (dep[p->v]) continue;
    dep[p->v] = dep[a] + 1;
    dfs(p->v, a);
    if (!dp[0][p->v] && !dp[1][p->v]) {
      dp[0][a] = dp[1][a] = 0;
      return;
    }
    if (dp[0][p->v] && dp[1][p->v])
      dp[0][a] = dp[1][a] = 1;
    else if (dp[1][p->v])
      lks++, lks &= 1;
  }
  if (d[a] == -1)
    dp[0][a] = dp[1][a] = 1;
  else
    dp[d[a] ^ lks][a] = 1;
}
int otp[300005], top = 0;
void solve(int a, int tp) {
  int lks = 0, ns = 0, ntp = 0;
  for (edge *p = h[a]; p; p = p->next) {
    if (dep[p->v] != dep[a] + 1) continue;
    if (dp[0][p->v] && dp[1][p->v])
      ns = p->v;
    else if (dp[1][p->v])
      lks++;
  }
  lks &= 1;
  if (d[a] != -1) ntp = d[a] ^ tp ^ lks;
  for (edge *p = h[a]; p; p = p->next) {
    if (dep[p->v] != dep[a] + 1) continue;
    int t = ntp;
    if (p->v != ns)
      if (dp[0][p->v])
        t = 0;
      else
        t = 1;
    if (t) otp[top++] = p->id;
    solve(p->v, t);
  }
}
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", &d[i]);
  for (int i = 1; i <= m; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    if (u > v) swap(u, v);
    eg[i].x = u, eg[i].y = v, eg[i].id = i;
  }
  sort(eg + 1, eg + m + 1);
  for (int i = 1; i <= m; i++)
    if (i == 1 || eg[i - 1] < eg[i])
      addedge(eg[i].x, eg[i].y, eg[i].id), addedge(eg[i].y, eg[i].x, eg[i].id);
  dep[1] = 1;
  dfs(1, 0);
  if (!dp[0][1])
    printf("-1\n");
  else {
    solve(1, 0);
    printf("%d\n", top);
    for (int i = 0; i < top; i++) printf("%d\n", otp[i]);
  }
  return 0;
}
