2 0
 100000 0
 8 9
1 2
2 3
3 4
4 1
5 6
6 7
7 8
8 5
6 8
 2 1
1 2
 11 9
5 9
8 5
11 3
11 1
3 4
7 11
3 1
11 2
7 2
 7 9
7 3
7 4
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 7 5
5 4
7 3
7 1
6 7
3 1
 7 8
1 2
2 3
3 4
4 1
3 5
5 6
6 7
7 3
 6 9
1 2
2 3
1 4
4 2
5 2
5 3
4 5
6 4
6 5
 7 9
1 2
2 4
4 3
3 1
2 3
4 5
5 6
6 7
7 4
 1 0
 6 7
1 2
2 3
3 1
3 4
4 5
5 6
6 4
 4 5
1 2
2 3
3 4
4 1
1 3
 100000 3
99998 99999
99999 100000
100000 99998

0

 0

 4
1 2 3 4 
 0

 6
3 4 6 7 8 9 
 9
1 2 3 4 5 6 7 8 9 
 3
2 3 5 
 8
1 2 3 4 5 6 7 8 
 0

 4
6 7 8 9 
 0

 6
1 2 3 5 6 7 
 0

 3
1 2 3 

#include <bits/stdc++.h>
using namespace std;
int Adj[100010], V[100010 * 2], nxt[100010 * 2], c;
void AddEdge(int u, int v) {
  c++;
  V[c] = v, nxt[c] = Adj[u];
  Adj[u] = c;
}
int vis[100010];
int x[100010], y[100010], id[100010], dfn[100010], low[100010], dcnt, r,
    ans[100010], cnt, n, m;
void Tarjan(int u, int p) {
  dcnt++;
  dfn[u] = low[u] = dcnt;
  for (int i = Adj[u]; i; i = nxt[i]) {
    int v = V[i], tmp = r;
    if (v == p) continue;
    if (!dfn[v]) {
      r++;
      x[r] = u, y[r] = v, id[r] = (i + 1) / 2;
      Tarjan(v, u);
      if (low[v] >= dfn[u]) {
        int f = 1, R = r, R1 = r;
        while (r != tmp) {
          vis[x[r]]++, vis[y[r]]++;
          r--;
        }
        while (R1 != tmp) {
          if (vis[x[R1]] != 2 || vis[y[R1]] != 2) {
            f = 0;
            break;
          }
          R1--;
        }
        while (R != tmp) {
          if (f) ans[cnt++] = id[R];
          vis[x[R]] = vis[y[R]] = 0;
          R--;
        }
        r = tmp;
      }
      low[u] = min(low[u], low[v]);
    } else {
      low[u] = min(low[u], dfn[v]);
      if (dfn[v] < dfn[u]) {
        r++;
        x[r] = u, y[r] = v, id[r] = (i + 1) / 2;
      }
    }
  }
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1, u, v; i <= m; i++) {
    scanf("%d%d", &u, &v);
    AddEdge(u, v);
    AddEdge(v, u);
  }
  Tarjan(1, 0);
  sort(ans, ans + cnt);
  printf("%d\n", cnt);
  for (int i = 0; i < cnt; i++) printf("%d ", ans[i]);
  printf("\n");
}
