2 0
 100000 0
 8 9
1 2
2 3
3 4
4 1
5 6
6 7
7 8
8 5
6 8
 2 1
1 2
 11 9
5 9
8 5
11 3
11 1
3 4
7 11
3 1
11 2
7 2
 7 9
7 3
7 4
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 7 5
5 4
7 3
7 1
6 7
3 1
 7 8
1 2
2 3
3 4
4 1
3 5
5 6
6 7
7 3
 6 9
1 2
2 3
1 4
4 2
5 2
5 3
4 5
6 4
6 5
 7 9
1 2
2 4
4 3
3 1
2 3
4 5
5 6
6 7
7 4
 1 0
 6 7
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 4 5
1 2
2 3
3 4
4 1
1 3
 100000 3
99998 99999
99999 100000
100000 99998

0

 0

 4
1 2 3 4 
 0

 6
3 4 6 7 8 9 
 9
1 2 3 4 5 6 7 8 9 
 3
2 3 5 
 8
1 2 3 4 5 6 7 8 
 0

 4
6 7 8 9 
 0

 6
1 2 3 5 6 7 
 0

 3
1 2 3 

#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;
}
