#include <bits/stdc++.h>
using namespace std;
const int MN = 100010;
int N, M;
vector<int> adj[MN], U, V;
int tin[MN], bck[MN], id[MN], timer, bcnt;
stack<int> stk;
void dfs(int u, int fe, bool root) {
  tin[u] = timer++;
  bck[u] = tin[u];
  for (int i = 0; i < adj[u].size(); i++) {
    int e = adj[u][i];
    int v = U[e] + V[e] - u;
    if (tin[v] == -1) {
      stk.push(e);
      dfs(v, e, false);
      bck[u] = min(bck[u], bck[v]);
      if (bck[v] >= tin[u]) {
        while (1) {
          int t = stk.top();
          stk.pop();
          id[t] = bcnt;
          if (t == e) break;
        }
        bcnt++;
      }
    } else if (tin[v] < tin[u]) {
      if (e != fe) stk.push(e);
      bck[u] = min(bck[u], tin[v]);
    }
  }
}
vector<int> C[MN], X, sol;
int main() {
  scanf("%d %d", &N, &M);
  for (int i = 0; i < M; i++) {
    int u, v;
    scanf("%d %d", &u, &v);
    u--;
    v--;
    adj[u].push_back(i);
    adj[v].push_back(i);
    U.push_back(u);
    V.push_back(v);
  }
  memset(tin, -1, sizeof(tin));
  for (int i = 0; i < N; i++)
    if (tin[i] == -1) {
      dfs(i, -1, true);
    }
  for (int i = 0; i < M; i++) {
    C[id[i]].push_back(i);
  }
  int ans = 0;
  for (int i = 0; i < bcnt; i++) {
    X.clear();
    for (int j = 0; j < C[i].size(); j++) {
      X.push_back(U[C[i][j]]);
      X.push_back(V[C[i][j]]);
    }
    sort(X.begin(), X.end());
    X.resize(unique(X.begin(), X.end()) - X.begin());
    if (X.size() == C[i].size()) {
      for (int j = 0; j < C[i].size(); j++) sol.push_back(C[i][j]);
    }
  }
  sort(sol.begin(), sol.end());
  printf("%d\n", sol.size());
  for (int i = 0; i < sol.size(); i++) {
    printf("%d ", sol[i] + 1);
  }
}
