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 <typename T1, typename T2>
inline void chkmin(T1 &x, T2 y) {
  if (x > y) x = y;
}
template <typename T1, typename T2>
inline void chkmax(T1 &x, T2 y) {
  if (x < y) x = y;
}
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) {
    pos = 0, len = fread(buf, 1, buf_size, stdin);
  }
  if (pos == len) {
    return -1;
  }
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) {
    c = getChar();
  }
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
const int MAXN = 300001;
int n, m;
int st[MAXN];
int a[MAXN], b[MAXN];
int step[MAXN];
bool need[MAXN];
bool used[MAXN];
bool ayw[MAXN];
vector<int> v[MAXN];
map<pair<int, int>, int> who;
vector<int> sons[MAXN];
int dp[MAXN][2];
bool bad[MAXN];
int dp1[MAXN][2];
int main() {
  n = readInt(), m = readInt();
  for (int i = 0; i < n; i++) {
    st[i] = readInt();
  }
  for (int i = 0; i < m; i++) {
    a[i] = readInt(), b[i] = readInt();
    a[i]--, b[i]--;
    step[a[i]]++;
    step[b[i]]++;
    who[make_pair(a[i], b[i])] = i;
    who[make_pair(b[i], a[i])] = i;
  }
  for (int i = 0; i < n; i++) {
    if (st[i] != -1) {
      if (step[i] % 2 != st[i]) {
        need[i] = true;
      }
    } else {
      ayw[i] = true;
    }
  }
  for (int i = 0; i < m; i++) {
    if (need[a[i]] && need[b[i]]) {
      need[a[i]] = false;
      need[b[i]] = false;
      used[i] = true;
      continue;
    }
    if (need[a[i]] && ayw[b[i]]) {
      need[a[i]] = false;
      used[i] = true;
      continue;
    }
    if (need[b[i]] && ayw[a[i]]) {
      need[b[i]] = false;
      used[i] = true;
      continue;
    }
  }
  for (int i = 0; i < m; i++) {
    if (!used[i]) {
      v[a[i]].push_back(b[i]);
      v[b[i]].push_back(a[i]);
    }
  }
  for (int i = 0; i < n; i++) {
    if (!need[i]) {
      set<int> s;
      for (auto x : v[i]) {
        if (need[x]) {
          s.insert(x);
        }
      }
      while ((int)(s).size() >= 2) {
        int as = *s.begin();
        s.erase(as);
        int bs = *s.begin();
        ;
        s.erase(bs);
        need[as] = false;
        need[bs] = false;
        used[who[make_pair(as, i)]] = true;
        used[who[make_pair(bs, i)]] = true;
      }
    }
  }
  for (int i = 0; i < n; i++) {
    if (!need[i]) {
      set<int> s;
      for (auto x : v[i]) {
        if (need[x]) {
          s.insert(x);
        }
      }
      if ((int)(s).size() == 1) {
        cout << "opa" << endl;
        bad[i] = true;
      }
    }
  }
  for (int i = 0; i < n; i++) {
    if (bad[i]) {
      for (auto xx : v[i]) {
        if (bad[xx]) {
          bad[i] = false;
          bad[xx] = false;
          for (auto x : v[i]) {
            if (need[x]) {
              used[who[make_pair(x, i)]] = true;
              need[x] = false;
              break;
            }
          }
          for (auto x : v[xx]) {
            if (need[x]) {
              used[who[make_pair(x, xx)]] = true;
              need[x] = false;
              break;
            }
          }
          break;
        }
      }
    }
  }
  for (int i = 0; i < n; i++) {
    if (need[i]) {
      writeInt(-1, '\n');
      return 0;
    }
  }
  vector<int> ans;
  for (int i = 0; i < m; i++) {
    if (!used[i]) {
      ans.push_back(i + 1);
    }
  }
  writeInt((int)(ans).size(), '\n');
  for (auto x : ans) {
    writeInt(x, ' ');
  }
  writeChar('\n');
  return 0;
}
