#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using vi = vector<int>;
int n, m;
vector<vector<pii> > ed;
int Time;
vi num, st;
template <class F>
int dfs(int at, int par, F f) {
  int me = num[at] = ++Time, e, y, top = me;
  for (auto& pa : ed[at])
    if (pa.second != par) {
      tie(y, e) = pa;
      if (num[y]) {
        top = min(top, num[y]);
        if (num[y] < me) st.push_back(e);
      } else {
        int si = st.size();
        int up = dfs(y, e, f);
        top = min(top, up);
        if (up == me) {
          st.push_back(e);
          f(vi(st.begin() + si, st.end()));
          st.resize(si);
        } else if (up < me)
          st.push_back(e);
      }
    }
  return top;
}
template <class F>
void bicomps(F f) {
  num.assign(ed.size(), 0);
  for (int i = 0; i < n; ++i)
    if (!num[i]) dfs(i, -1, f);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  scanf("%d %d", &n, &m);
  ed.resize(n);
  vector<pii> edges(m);
  int u, v;
  for (int i = 0; i < m; ++i) {
    scanf("%d %d", &u, &v);
    --u;
    --v;
    ed[u].emplace_back(v, i);
    ed[v].emplace_back(u, i);
    edges[i] = {u, v};
  }
  vi valid;
  bicomps([&](const vi& edgelist) {
    vi verts;
    for (int x : edgelist) {
      verts.push_back(edges[x].first);
      verts.push_back(edges[x].second);
    }
    sort(begin(verts), end(verts));
    verts.resize(unique(begin(verts), end(verts)) - begin(verts));
    int num_verts = verts.size();
    int num_edges = edgelist.size();
    if (num_verts == num_edges) {
      for (int x : edgelist) valid.push_back(x);
    }
  });
  sort(begin(valid), end(valid));
  printf("%lu\n", valid.size());
  for (int x : valid) printf("%d ", x + 1);
  return 0;
}
