#include <bits/stdc++.h>
using namespace std;
const int mn = 3e5 + 10;
int d[mn];
bool vis[mn];
vector<int> g[mn], in[mn], u;
void dfs(int x) {
  vis[x] = 1;
  for (int i = 0; i < g[x].size(); i++) {
    int y = g[x][i];
    if (vis[y]) continue;
    dfs(y);
    if (d[y] == 1) {
      d[x] ^= 1;
      u.push_back(in[x][i]);
    }
  }
}
int main() {
  int n, m, i, a, b;
  scanf("%d%d", &n, &m);
  int st = 1;
  for (i = 1; i <= n; i++) {
    scanf("%d", d + i);
    if (d[i] < 0) st = i;
  }
  for (i = 0; i < m; i++) {
    scanf("%d%d", &a, &b);
    g[a].push_back(b);
    g[b].push_back(a);
    in[a].push_back(i + 1);
    in[b].push_back(i + 1);
  }
  dfs(st);
  if (d[st] == 1)
    printf("-1");
  else {
    printf("%d\n", u.size());
    for (int x : u) printf("%d\n", x);
  }
}
