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;
const int N = 100002;
int n, m;
vector<vector<pair<int, int>>> g(N);
map<int, bool> bridge;
int ndfn, lowLink[N], dfn[N], comp[N];
vector<vector<int>> comps;
stack<int> stk;
bool inStack[N], vis[N];
void tarjan(int node, int p) {
  lowLink[node] = dfn[node] = ndfn++;
  stk.push(node), inStack[node] = 1;
  for (int i = 0; i <= ((int)(g[node]).size()) - 1; ++i) {
    int ch = g[node][i].first;
    if (ch == p) continue;
    if (dfn[ch] == -1) {
      tarjan(ch, node);
      lowLink[node] = min(lowLink[node], lowLink[ch]);
      if (lowLink[ch] > dfn[node]) bridge[g[node][i].second] = true;
    } else if (inStack[ch])
      lowLink[node] = min(lowLink[node], dfn[ch]);
  }
  if (lowLink[node] == dfn[node]) {
    comps.push_back(vector<int>());
    int x = -1;
    while (x != node) {
      x = stk.top(), stk.pop(), inStack[x] = 0;
      comps.back().push_back(x);
      comp[x] = ((int)(comps).size()) - 1;
    }
  }
}
void scc() {
  memset(dfn, -1, sizeof dfn);
  memset(comp, -1, sizeof comp);
  for (int i = 1; i <= n; ++i)
    if (dfn[i] == -1) tarjan(i, -1);
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; ++i) {
    int x, y;
    scanf("%d%d", &x, &y);
    g[x].push_back({y, i});
    g[y].push_back({x, i});
  }
  scc();
  set<int> ans;
  for (int i = 0; i <= ((int)(comps).size()) - 1; ++i)
    if (((int)(comps[i]).size()) > 2) {
      int edges = 0;
      bool ok = true;
      for (int j : comps[i]) {
        int d = ((int)(g[j]).size());
        for (pair<int, int> p : g[j]) d -= bridge[p.second];
        ok &= d % 2 == 0;
        edges += d;
      }
      if (ok and (((int)(comps[i]).size()) == 3 or
                  edges / 2 < 1ll * ((int)(comps[i]).size()) *
                                  (((int)(comps[i]).size()) - 1) / 2)) {
        for (int j : comps[i])
          for (pair<int, int> p : g[j])
            if (!bridge[p.second]) ans.insert(p.second);
      }
    }
  cout << (((int)(ans).size())) << endl;
  for (int i : ans) printf("%d ", i);
}
