#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int deg[N];
int low[N], dfn[N], timer = 0;
vector<int> edges_stack;
pair<int, int> edges[N];
set<int> ans;
vector<pair<int, int> > adj[N];
bool vis[N];
void process_block(int stop) {
  if (edges_stack.empty()) return;
  set<int> nodes;
  set<int> curr_edges;
  while (!edges_stack.empty()) {
    int curr = edges_stack.back();
    edges_stack.pop_back();
    int u = edges[curr].first;
    int v = edges[curr].second;
    nodes.insert(u);
    nodes.insert(v);
    vis[u] = vis[v] = 1;
    if (curr == stop) break;
  }
  bool ok = 1;
  for (int nd : nodes) {
    for (auto A : adj[nd]) {
      int v = A.second;
      int e = A.first;
      if (vis[v]) {
        curr_edges.insert(e);
        deg[nd]++;
      }
    }
  }
  for (int nd : nodes) {
    if (deg[nd] != 2) ok = 0;
    deg[nd] = vis[nd] = 0;
  }
  if (ok) {
    for (int e : curr_edges) ans.insert(e);
  }
}
void dfs(int u, int p) {
  low[u] = dfn[u] = ++timer;
  int root_children = 0;
  for (pair<int, int> A : adj[u]) {
    int v = A.second;
    int e = A.first;
    if (!dfn[v]) {
      root_children++;
      edges_stack.push_back(e);
      dfs(v, u);
      low[u] = min(low[u], low[v]);
      if ((p != -1 && dfn[u] <= low[v]) || (p == -1 && root_children > 1)) {
        process_block(e);
      }
    } else if (v != p) {
      if (dfn[v] < low[u]) {
        low[u] = dfn[v];
        edges_stack.push_back(e);
      }
    }
  }
}
int main() {
  int n, m;
  scanf("%d %d", &n, &m);
  for (int i = 0; i < m; i++) {
    int u, v;
    scanf("%d %d", &u, &v);
    adj[u].push_back({i + 1, v});
    adj[v].push_back({i + 1, u});
    edges[i + 1] = {u, v};
  }
  for (int i = 1; i <= n; i++) {
    if (!dfn[i]) {
      dfs(i, -1);
      process_block(-1);
    }
  }
  printf("%d\n", ans.size());
  for (int A : ans) printf("%d ", A);
  return 0;
}
