#include <bits/stdc++.h>

using namespace std;


using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}

struct UnionFind {
  vector< int > data;

  UnionFind(int sz) {
    data.assign(sz, -1);
  }

  bool unite(int x, int y) {
    x = find(x), y = find(y);
    if(x == y) return (false);
    if(data[x] > data[y]) swap(x, y);
    data[x] += data[y];
    data[y] = x;
    return (true);
  }

  int find(int k) {
    if(data[k] < 0) return (k);
    return (data[k] = find(data[k]));
  }

  int size(int k) {
    return (-data[find(k)]);
  }
};

template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WeightedGraph = vector< Edges< T > >;
using UnWeightedGraph = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;

int main() {
  int N, M;
  cin >> N >> M;
  vector< pair< int, int > > mx(N);
  cin >> mx;
  sort(begin(mx), end(mx));
  mx.emplace_back(inf, 0);

  vector< int > diff(N + 1);
  diff[0] = mx[0].second;
  for(int i = 1; i < N; i++) diff[i] = mx[i - 1].second ^ mx[i].second;
  diff[N] = mx[N - 1].second;

  // 連結成分の1の個数が偶数個なら勝ちます
  UnionFind uf(N + 1);
  WeightedGraph< int > g(N + 1);

  for(int i = 0; i < M; i++) {
    int l, r;
    cin >> l >> r;
    int latte = lower_bound(begin(mx), end(mx), make_pair(l, -1)) - begin(mx);
    int malta = lower_bound(begin(mx), end(mx), make_pair(r, inf)) - begin(mx);
    if(latte >= malta) continue;
    if(uf.unite(latte, malta)) {
      g[latte].emplace_back(malta, i + 1);
      g[malta].emplace_back(latte, i + 1);
    }
  }

  vector< int > ans;
  auto dfs = MFP([&](auto dfs, int idx, int par) -> bool {
    bool uku = diff[idx];
    for(auto &to : g[idx]) {
      if(to == par) continue;
      auto ret = dfs(to, idx);
      if(ret) ans.emplace_back(to.cost);
      uku ^= ret;
    }
    return uku;
  });

  for(int i = 0; i < N + 1; i++) {
    if(uf.find(i) == i && dfs(i, -1)) {
      cout << -1 << endl;
      return 0;
    }
  }

  sort(begin(ans), end(ans));
  cout << ans.size() << endl;
  cout << ans << endl;
}


Measured memory_bytes: 9072