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;
template <class T>
inline void read(T &res) {
  char c;
  T flag = 1;
  while ((c = getchar()) < '0' || c > '9')
    if (c == '-') flag = -1;
  res = c - '0';
  while ((c = getchar()) >= '0' && c <= '9') res = res * 10 + c - '0';
  res *= flag;
}
void wenjian() {
  freopen("concatenation.in", "r", stdin);
  freopen("concatenation.out", "w", stdout);
}
void tempwj() {
  freopen("hash.in", "r", stdin);
  freopen("hash.out", "w", stdout);
}
long long gcd(long long a, long long b) { return b == 0 ? a : gcd(b, a % b); }
long long qpow(long long a, long long b, long long mod) {
  a %= mod;
  long long ans = 1;
  while (b) {
    if (b & 1) ans = ans * a % mod;
    a = a * a % mod;
    b >>= 1;
  }
  return ans;
}
struct chongzai {
  int c;
  bool operator<(const chongzai &b) const { return c > b.c; }
} sss;
const int maxn = 6e5 + 177;
const int maxm = 1e6 + 177;
const long long mod = 0x3f3f3f3f3f3f3f3f;
const int inf = 0x3f3f3f3f;
const long long INF = 0x3f3f3f3f3f3f3f3f;
struct Node {
  int next;
  int to;
  int vul;
} edge[maxn];
int vis[maxn];
int head[maxn];
int tot;
vector<int> ans;
int n, m;
int a[maxn];
void add(int from, int to) {
  edge[++tot].next = head[from];
  edge[tot].to = to;
  head[from] = tot;
}
void init() {
  for (int i = 0; i < n + 17; i++) {
    head[i] = 0;
    vis[i] = 0;
  }
  tot = 0;
}
void dfs(int x) {
  vis[x] = 1;
  for (int i = head[x]; i; i = edge[i].next) {
    int y = edge[i].to;
    if (vis[y]) continue;
    dfs(y);
    if (a[y] == 1) {
      ans.push_back((i + 1) / 2);
      a[y] = 0;
      if (a[x] != -1) {
        a[x] = 1 - a[x];
      }
    }
  }
}
int main() {
  scanf("%d%d", &n, &m);
  init();
  int num1 = 0;
  bool pp = false;
  int index = 1;
  for (int i = 1; i <= n; i++) {
    scanf("%d", &a[i]);
    if (a[i] == 1) {
      num1++;
    }
    if (a[i] == -1) {
      pp = true;
      index = i;
    }
  }
  int be, en;
  for (int i = 1; i <= m; i++) {
    scanf("%d%d", &be, &en);
    add(be, en);
    add(en, be);
  }
  if (num1 % 2 == 1 && !pp) {
    printf("-1");
    return 0;
  }
  dfs(index);
  printf("%d\n", ans.size());
  for (int i = 0; i < ans.size(); i++) {
    printf("%d ", ans[i]);
  }
  printf("\n");
}
