#include <bits/stdc++.h>
using namespace std;
const int maxn = 100010;
int n, m;
int low[maxn], dfn[maxn], v[maxn << 1], A[maxn];
int nxt[maxn << 1], head[maxn], belong[maxn], a[maxn], vis[maxn << 1];
stack<int> s;
int indexs = 0, cnt = 0;
int ans = 0;
void add_edge(int x, int y) {
  static int N = 1;
  N++;
  v[N] = y;
  nxt[N] = head[x];
  head[x] = N;
}
void tarjan(int x, int fa) {
  dfn[x] = low[x] = ++indexs;
  for (int i = head[x]; i != -1; i = nxt[i]) {
    if (vis[i]) continue;
    vis[i] = vis[i ^ 1] = 1;
    s.push(i);
    if (!dfn[v[i]]) {
      tarjan(v[i], x);
      low[x] = min(low[x], low[v[i]]);
      if (low[v[i]] >= dfn[x]) {
        cnt++;
        int num = 0, bcnt = 0;
        while (1) {
          int tmp = s.top();
          s.pop();
          if (belong[v[tmp]] != cnt) belong[v[tmp]] = cnt, num++;
          if (belong[v[tmp ^ 1]] != cnt) belong[v[tmp ^ 1]] = cnt, num++;
          a[++bcnt] = tmp;
          if (tmp == i) break;
        }
        if (num == bcnt)
          for (int i = 1; i <= bcnt; i++) A[++ans] = a[i];
      }
    } else
      low[x] = min(low[x], dfn[v[i]]);
  }
}
int main() {
  memset(head, -1, sizeof(head));
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; i++) {
    int x, y;
    scanf("%d%d", &x, &y);
    add_edge(x, y);
    add_edge(y, x);
  }
  for (int i = 1; i <= n; i++)
    if (!dfn[i]) tarjan(i, 0);
  sort(A + 1, A + 1 + ans);
  printf("%d\n", ans);
  for (int i = 1; i <= ans; i++) cout << (A[i] >> 1) << " ";
  return 0;
}
