#include <bits/stdc++.h>
using namespace std;
struct node {
  int to, id;
  node *nxt;
} edges[100000 * 2 + 5];
node *ncnt = &edges[0], *Adj[100000 + 5];
int n, m;
int fro[100000 + 5], to[100000 + 5];
int dfn[100000 + 5], low[100000 + 5], tcnt = 0;
stack<int> sta;
set<int> st;
vector<int> need, ans;
void AddEdge(int u, int v, int id) {
  node *p = ++ncnt;
  p->to = v;
  p->id = id;
  p->nxt = Adj[u];
  Adj[u] = p;
  node *q = ++ncnt;
  q->to = u;
  q->id = id;
  q->nxt = Adj[v];
  Adj[v] = q;
}
void Tarjan(int u, int fa) {
  dfn[u] = low[u] = ++tcnt;
  for (node *p = Adj[u]; p != NULL; p = p->nxt) {
    int v = p->to;
    if (dfn[v] == 0) {
      sta.push(p->id);
      Tarjan(v, u);
      low[u] = min(low[u], low[v]);
      if (low[v] >= dfn[u]) {
        int tp;
        st.clear();
        need.clear();
        do {
          tp = sta.top();
          sta.pop();
          st.insert(fro[tp]);
          st.insert(to[tp]);
          need.push_back(tp);
        } while (sta.empty() == false &&
                 (fro[tp] != fro[p->id] || to[tp] != to[p->id]));
        if (st.size() == need.size())
          for (int i = 0; i < (int)need.size(); i++) ans.push_back(need[i]);
      }
    } else if (v != fa) {
      if (dfn[u] > dfn[v]) sta.push(p->id);
      low[u] = min(low[u], dfn[v]);
    }
  }
}
int main() {
  scanf("%d %d", &n, &m);
  int u, v;
  for (int i = 1; i <= m; i++) {
    scanf("%d %d", &u, &v);
    AddEdge(u, v, i);
    fro[i] = u, to[i] = v;
  }
  for (int i = 1; i <= n; i++)
    if (dfn[i] == 0) Tarjan(i, -1);
  printf("%d\n", (int)ans.size());
  sort(ans.begin(), ans.end());
  for (int i = 0; i < (int)ans.size(); i++)
    if (i == 0)
      printf("%d", ans[i]);
    else
      printf(" %d", ans[i]);
  printf("\n");
  return 0;
}
