#include <bits/stdc++.h>
using namespace std;
const int N = 400000;
int low[N], idx[N], dfs;
vector<vector<pair<int, int> > > g;
int n, e;
set<pair<int, int> > rem;
bool br[N];
void DFS(int u, int p) {
  low[u] = idx[u] = ++dfs;
  vector<pair<int, int> > seg;
  for (auto vv : g[u]) {
    auto v = vv.first;
    if (!idx[v]) {
      int l = dfs + 1;
      DFS(v, u);
      int r = dfs;
      low[u] = min(low[u], low[v]);
      if (low[v] >= idx[u]) seg.push_back({l, r});
      if (low[v] > idx[u]) br[vv.second] = true;
    } else if (v != p)
      low[u] = min(low[u], idx[v]);
  }
  if (seg.empty()) return;
  int before = g.size();
  g.resize(g.size() + seg.size());
  for (int i = 0; i < g[u].size(); ++i) {
    int v = g[u][i].first;
    if (idx[v] >= seg[0].first && low[v] >= idx[u]) {
      auto it = upper_bound(seg.begin(), seg.end(), make_pair(idx[v], N)) -
                seg.begin();
      --it;
      if (idx[v] > seg[it].second) continue;
      int w = it + before;
      g[w].push_back(make_pair(v, g[u][i].second));
      g[v].push_back(make_pair(w, g[u][i].second));
      rem.insert({min(u, v), max(u, v)});
    }
  }
}
bool vis[N];
int cnt;
set<int> E;
void DFS(int u) {
  vis[u] = true;
  ++cnt;
  for (auto vv : g[u]) {
    auto v = vv.first;
    E.insert(vv.second);
    if (!vis[v]) DFS(v);
  }
}
int main() {
  scanf("%d%d", &n, &e);
  g.resize(n);
  g.reserve(2 * n);
  for (int i = 0, a, b; i < e; ++i) {
    scanf("%d%d", &a, &b);
    --a;
    --b;
    g[a].push_back({b, i});
    swap(a, b);
    g[a].push_back({b, i});
  }
  for (int i = 0; i < n; ++i)
    if (!low[i]) DFS(i, -1);
  for (int i = 0; i < g.size(); ++i) {
    for (int j = 0; j < g[i].size(); ++j) {
      int u = i;
      int v = g[i][j].first;
      if (u > v) swap(u, v);
      if (br[g[i][j].second] || rem.find(make_pair(u, v)) != rem.end()) {
        g[i][j] = g[i].back();
        g[i].pop_back();
        --j;
      }
    }
  }
  set<int> sol;
  for (int i = 0; i < g.size(); ++i)
    if (!vis[i]) {
      E.clear();
      cnt = 0;
      DFS(i);
      if (E.size() == cnt) {
        for (auto x : E) sol.insert(x);
      }
    }
  printf("%d\n", (int)sol.size());
  for (auto x : sol) printf("%d ", x + 1);
  return 0;
}
