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>
#pragma GCC optimize(3, "inline", "Ofast")
using namespace std;
vector<int> ans;
int n, m, to[500010], deep[500010];
int nxt[500010], hd[500010], fa[100010], tofa[500010], num = -1, cf[500010];
bool tree[500010], vis[100010];
void add(int u, int v) {
  nxt[++num] = hd[u];
  to[num] = v;
  hd[u] = num;
  nxt[++num] = hd[v];
  to[num] = u;
  hd[v] = num;
}
void dfs1(int pos, int f, int dp) {
  fa[pos] = f;
  vis[pos] = 1;
  deep[pos] = dp;
  for (int i = hd[pos]; i != -1; i = nxt[i])
    if (!vis[to[i]]) {
      tofa[to[i]] = i, tree[i] = 1;
      dfs1(to[i], pos, dp + 1);
    }
  return;
}
void dfs(int pos) {
  vis[pos] = 1;
  for (int i = hd[pos]; i != -1; i = nxt[i])
    if (tree[i]) {
      dfs(to[i]);
      cf[pos] += cf[to[i]];
    }
  return;
}
int main() {
  memset(hd, -1, sizeof hd);
  memset(nxt, -1, sizeof nxt);
  scanf("%d%d", &n, &m);
  for (int i = 1, a, b; i <= m; i++) {
    scanf("%d%d", &a, &b);
    add(a, b);
  }
  for (int i = 1; i <= n; i++)
    if (!vis[i]) dfs1(i, 0, 1);
  for (int i = 0, u, v; i <= num; i += 2) {
    if (tree[i] || tree[i + 1])
      continue;
    else
      u = to[i], v = to[i + 1];
    if (deep[u] < deep[v]) swap(u, v);
    cf[u]++;
    cf[v]--;
  }
  memset(vis, 0, sizeof vis);
  for (int i = 1; i <= n; i++)
    if (!vis[i]) dfs(i);
  for (int i = 0, u, v; i <= num; i += 2) {
    if (tree[i] || tree[i + 1]) continue;
    u = to[i], v = to[i + 1];
    if (deep[u] < deep[v]) swap(u, v);
    if ([u, v]() {
          for (int tmp = u; tmp != v; tmp = fa[tmp])
            if (cf[tmp] != 1) return false;
          return true;
        }()) {
      ans.push_back((i + 2) / 2);
      while (u != v) {
        ans.push_back((tofa[u] + 2) / 2);
        u = fa[u];
      }
    }
  }
  sort(ans.begin(), ans.end());
  printf("%llu\n", ans.size());
  for (const int &e : ans) printf("%d ", e);
  printf("\n");
  return 0;
}
