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;
class mstream {
 private:
  int res = 0;
  bool right = 0, sign = 0, space = 0, zero = 0;
  int width = 0, precision = 0, maxwidth = 1e6;
  string interval = "";
  const char* formstr(bool ri, bool si, bool sp, bool ze, bool wi, bool pr,
                      string ty) {
    string f = "%";
    if (ri && right) f += "-";
    if (si && sign) f += "+";
    if (sp && space) f += " ";
    if (ze && zero) f += "0";
    if (wi) f += "*";
    if (pr) f += ".*";
    f += ty;
    f += "%s";
    return f.c_str();
  }

 public:
  operator int() { return res; }
  mstream() {}
  mstream operator()() {
    res = 0;
    return *this;
  }
  mstream setright(bool n = 1) {
    right = n;
    return *this;
  }
  mstream setleft(bool n = 1) {
    right = !n;
    return *this;
  }
  mstream setsign(bool n = 1) {
    sign = n;
    return *this;
  }
  mstream notsign(bool n = 1) {
    sign = !n;
    return *this;
  }
  mstream setspace(bool n = 1) {
    space = n;
    return *this;
  }
  mstream notspace(bool n = 1) {
    space = !n;
    return *this;
  }
  mstream setzero(bool n = 1) {
    zero = n;
    return *this;
  }
  mstream notzero(bool n = 1) {
    zero = !n;
    return *this;
  }
  mstream setwidth(int n = 0) {
    width = n;
    return *this;
  }
  mstream setprecision(int n = 6) {
    precision = n;
    return *this;
  }
  mstream setmaxwidth(int n = 1e6) {
    maxwidth = n;
    return *this;
  }
  mstream setinterval(string n = " ") {
    interval = n;
    return *this;
  }
  mstream notinterval(string n = "") {
    interval = n;
    return *this;
  }
  mstream operator>>(int& x) {
    int r = scanf("%d", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(long long& x) {
    int r = scanf("%I64d", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(float& x) {
    int r = scanf("%f", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(double& x) {
    int r = scanf("%lf", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(char& x) {
    int r = scanf("%c", &x);
    if (r != EOF) res += r;
    return *this;
  }
  mstream operator>>(string& x) {
    char s[maxwidth + 1];
    int r = scanf("%s", s);
    if (r != EOF) x = s, res += r;
    return *this;
  }
  mstream operator<<(int x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 0, "d"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(long long x) {
    int r =
        printf(formstr(1, 1, 1, 1, 1, 0, "I64d"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(float x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 1, "f"), width, precision, x,
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(double x) {
    int r = printf(formstr(1, 1, 1, 1, 1, 1, "lf"), width, precision, x,
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(char x) {
    int r = printf(formstr(1, 0, 0, 1, 1, 0, "c"), width, x, interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
  mstream operator<<(string x) {
    int r = printf(formstr(1, 0, 0, 1, 1, 1, "s"), width, maxwidth, x.c_str(),
                   interval.c_str());
    if (r > 0) res += r;
    return *this;
  }
};
mstream mstr = mstream();
int n, m;
vector<int> d;
vector<vector<pair<int, int> > > g;
vector<bool> b;
set<int> ans;
bool dfs1(int v) {
  if (b[v]) return false;
  b[v] = true;
  int deg = 0;
  for (pair<int, int> i : g[v])
    if (dfs1(i.second)) {
      ans.insert(i.first);
      deg = (deg + 1) % 2;
    }
  if (d[v] >= 0 && d[v] != deg)
    return true;
  else
    return false;
}
int dfs2(int v) {
  if (b[v]) return 0;
  b[v] = true;
  int res = 0;
  for (pair<int, int> i : g[v]) {
    int p = dfs2(i.second);
    res += p;
    if (p % 2 == 1) ans.insert(i.first);
  }
  if (d[v] == 1) res++;
  return res;
}
int main() {
  mstr >> n >> m;
  d.resize(n);
  int dm1 = -1;
  set<int> d1;
  for (long long i = 0, i_TO = n; i < i_TO; i++) {
    mstr >> d[i];
    if (d[i] == -1) dm1 = i;
    if (d[i] == 1) d1.insert(i);
  }
  g.resize(n);
  for (long long i = 0, i_TO = m; i < i_TO; i++) {
    int u, v;
    mstr >> u >> v;
    u--;
    v--;
    g[u].push_back(make_pair(i, v));
    g[v].push_back(make_pair(i, u));
  }
  if ((dm1 == -1) && (((int)((d1).size())) % 2 == 1)) mstr << -1, exit(0);
  b = vector<bool>(n);
  if (dm1 != -1)
    dfs1(dm1);
  else if (!d1.empty())
    dfs2(*d1.begin());
  mstr.setinterval("\n");
  mstr << ((int)((ans).size()));
  for (int k : ans) mstr << k + 1;
}
