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;
int in() {
  int x;
  scanf("%d", &x);
  return x;
}
long long lin() {
  long long x;
  scanf("%lld", &x);
  return x;
}
const int N = 100000;
int low[N], pre[N], visit[N];
vector<pair<int, int> > bridge;
int cnt;
vector<int> e[N];
void dfs(int now, int past) {
  visit[now] = 1;
  pre[now] = cnt++;
  low[now] = pre[now];
  for (int next : e[now]) {
    if (next == past) continue;
    if (pre[next] == -1) {
      dfs(next, now);
      if (low[next] == pre[next]) {
        bridge.push_back(pair<int, int>(min(now, next), max(now, next)));
      }
    }
    low[now] = min(low[now], low[next]);
  }
}
set<int> go;
void dfs2(int now) {
  visit[now] = 1;
  go.insert(now);
  for (int next : e[now]) {
    if (visit[next]) continue;
    dfs2(next);
  }
}
int main() {
  int n, m;
  cin >> n >> m;
  vector<pair<int, int> > eg(m);
  for (int i = 0; i < m; ++i) {
    int u = in() - 1, v = in() - 1;
    if (u > v) swap(u, v);
    eg[i] = pair<int, int>(u, v);
    e[u].push_back(v);
    e[v].push_back(u);
  }
  for (int i = 0; i < n; ++i) pre[i] = low[i] = -1;
  for (int i = 0; i < n; ++i) {
    if (!visit[i]) dfs(i, -1);
  }
  for (int i = 0; i < n; ++i) e[i].clear();
  set<pair<int, int> > br;
  for (pair<int, int> p : bridge) {
    br.insert(p);
  }
  for (int i = 0; i < m; ++i) {
    if (br.count(eg[i]) == 0) {
      e[eg[i].first].push_back(eg[i].second);
      e[eg[i].second].push_back(eg[i].first);
    }
  }
  for (int i = 0; i < n; ++i) visit[i] = 0;
  vector<int> onc(n);
  for (int i = 0; i < n; ++i) {
    if (visit[i]) continue;
    dfs2(i);
    bool ok = true;
    for (int x : go) {
      if (e[x].size() > 2) ok = false;
    }
    if (ok) {
      for (int x : go) onc[x] = 1;
    }
    go.clear();
  }
  vector<int> ans;
  for (int i = 0; i < m; ++i) {
    if (br.count(eg[i]) == 0 && onc[eg[i].first] && onc[eg[i].second]) {
      ans.push_back(i);
    }
  }
  cout << ans.size() << endl;
  for (int x : ans) printf("%d ", x + 1);
  cout << endl;
  return 0;
}
