#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 7;
struct edge {
  int t, nxt;
} e[N << 1];
int n, m, cnt = 1, T, tp, now, nume, numd;
int head[N], dfn[N], low[N], st[N], vis[N << 1], bl[N], a[N];
vector<int> ans;
void add(int u, int t) {
  e[++cnt].t = t;
  e[cnt].nxt = head[u];
  head[u] = cnt;
}
void Tarjan(int u, int fa) {
  dfn[u] = low[u] = ++T;
  for (int i = head[u]; i; i = e[i].nxt) {
    int t = e[i].t;
    if (t == fa || vis[i]) continue;
    vis[i] = vis[i ^ 1] = 1;
    st[++tp] = i;
    if (!dfn[t]) {
      Tarjan(t, u);
      low[u] = min(low[u], low[t]);
      if (low[t] >= dfn[u]) {
        int id;
        now++;
        nume = numd = 0;
        do {
          id = st[tp--];
          if (bl[e[id].t] != now) bl[e[id].t] = now, numd++;
          if (bl[e[id ^ 1].t] != now) bl[e[id ^ 1].t] = now, numd++;
          a[++nume] = id;
        } while (id != i);
        if (nume == numd)
          for (int i = 1; i <= nume; i++) ans.push_back(a[i] >> 1);
      }
    } else
      low[u] = min(low[u], dfn[t]);
  }
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1, u, v; i <= m; i++)
    scanf("%d%d", &u, &v), add(u, v), add(v, u);
  for (int i = 1; i <= n; i++)
    if (!dfn[i]) Tarjan(i, 0);
  sort(ans.begin(), ans.end());
  printf("%d\n", (int)ans.size());
  for (int i = 0; i < (int)ans.size(); i++) printf("%d ", ans[i]);
}
