#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline void read(T &x) {
  x = 0;
  int fu = 1;
  char c = getchar();
  while (c > 57 || c < 48) {
    if (c == 45) fu = -1;
    c = getchar();
  }
  while (c <= 57 && c >= 48) {
    x = (x << 3) + (x << 1) + c - 48;
    c = getchar();
  }
  x *= fu;
}
template <typename T>
inline void fprint(T x) {
  if (x < 0) putchar(45), x = -x;
  if (x > 9) fprint(x / 10);
  putchar(x % 10 + 48);
}
template <typename T>
inline void fprint(T x, char ch) {
  fprint(x);
  putchar(ch);
}
int n, m;
int a[300005];
int ck = 0, one = 0;
vector<pair<int, int> > vec[300005];
int fa[300005];
pair<int, int> f[300005];
int fd(int x) {
  if (fa[x] == x) return x;
  return fa[x] = fd(fa[x]);
}
bitset<300005> b;
int d[300005];
void dfs(int x, int pre) {
  f[x].first = pre;
  for (int i = 0; i < vec[x].size(); i++) {
    if (vec[x][i].first == pre) continue;
    d[x]++;
    f[vec[x][i].first].second = vec[x][i].second;
    dfs(vec[x][i].first, x);
  }
}
queue<int> q;
void bfs() {
  for (register int i = 1; i <= n; i++) {
    if (!d[i]) q.push(i);
  }
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    if (a[x]) b[f[x].second] = 1, a[f[x].first] ^= 1;
    d[f[x].first]--;
    if (!d[f[x].first]) q.push(f[x].first);
  }
}
int main() {
  read(n);
  read(m);
  for (int i = 1; i <= n; i++) {
    read(a[i]);
    if (~a[i])
      one ^= a[i];
    else
      ck = 1;
    fa[i] = i;
  }
  if (one && !ck) return printf("-1\n"), 0;
  for (register int i = 1; i <= n; i++) {
    if (a[i] == -1) {
      if (one)
        a[i] = 1, one = 0;
      else
        a[i] = 0;
    }
  }
  for (int i = 1; i <= m; i++) {
    int u, v;
    read(u);
    read(v);
    int uu = fd(u), vv = fd(v);
    if (uu ^ vv) {
      fa[uu] = vv;
      vec[u].push_back(make_pair(v, i));
      vec[v].push_back(make_pair(u, i));
    }
  }
  dfs(1, 0);
  bfs();
  fprint(b.count(), 10);
  for (int i = 1; i <= m; i++) {
    if (b[i]) fprint(i, 10);
  }
  return 0;
}
