#include <bits/stdc++.h>
using namespace std;
const int mod = 1000000007;
const long long int big = 1e18 + 10;
const long double pai = 3.141592653589793238462643383279502884197;
const long double eps = 1e-9;
template <class T, class U>
void mineq(T& a, U b) {
  if (a > b) {
    a = b;
  }
}
template <class T, class U>
void maxeq(T& a, U b) {
  if (a < b) {
    a = b;
  }
}
long long int gcd(long long int a, long long int b) {
  if (a % b == 0) {
    return b;
  } else
    return gcd(b, a % b);
}
long long int lcm(long long int a, long long int b) {
  return a / gcd(a, b) * b;
}
vector<vector<tuple<int, int, int>>> ko;
vector<tuple<int, int, int>> oya;
vector<int> d;
void make_tree(int per, int ter) {
  decltype(ko[ter].begin()) ita;
  for (auto itr = ko[ter].begin(); itr != ko[ter].end(); itr++) {
    if (get<0>(*itr) == per) {
      ita = itr;
    }
  }
  if (per != -1) {
    oya[ter] = (*ita);
    ko[ter].erase(ita);
  } else {
    oya[ter] = make_tuple(0, 0, 0);
  }
  for (auto it = ko[ter].begin(); it != ko[ter].end(); it++) {
    make_tree(ter, get<0>(*it));
  }
}
int solve(int ter) {
  int now = d[ter];
  for (auto it = ko[ter].begin(); it != ko[ter].end(); it++) {
    now += solve(get<0>(*it));
  }
  if (d[ter] == -1) {
    return 0;
  }
  if (now % 2 == 1) {
    get<2>(oya[ter]) = 1;
  }
  return now % 2;
}
int main(void) {
  int n, m, i;
  cin >> n >> m;
  vector<int> go(n);
  vector<int> ran(n, 0);
  d.resize(n);
  ko.resize(n);
  oya.resize(n);
  int roo = 0;
  for (i = 0; i < n; i++) {
    int in;
    cin >> in;
    if (in == -1) {
      roo = i;
    }
    d[i] = in;
    go[i] = i;
  }
  for (i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    int ma = a, mb = b;
    while (go[a] != a) {
      a = go[a];
    }
    while (go[b] != b) {
      b = go[b];
    }
    if (a == b) {
      continue;
    }
    if (ran[a] < ran[b]) {
      swap(a, b);
    }
    if (ran[a] == ran[b]) {
      ran[a]++;
    }
    go[b] = a;
    ko[ma].push_back(make_tuple(mb, i + 1, 0));
    ko[mb].push_back(make_tuple(ma, i + 1, 0));
  }
  make_tree(-1, roo);
  if (solve(roo) == 1) {
    cout << -1 << endl;
    return 0;
  }
  vector<int> ans;
  for (i = 0; i < n; i++) {
    if (get<2>(oya[i]) == 1) {
      ans.push_back(get<1>(oya[i]));
    }
  }
  sort(ans.begin(), ans.end());
  cout << ans.size() << endl;
  for (i = 0; i < ans.size(); i++) {
    cout << ans[i] << endl;
  }
  return 0;
}
