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;
const int N = 200005;
int num[N], low[N], vis[N], cor[N];
vector<pair<int, int> > g[N];
vector<int> S;
int ans[N], del[N];
int t, e;
void dfs(int u, int p) {
  low[u] = num[u] = t++;
  for (pair<int, int> x : g[u]) {
    int v = x.first;
    int id = x.second;
    if (num[v] == -1) {
      dfs(v, u);
      if (low[v] > num[u]) del[id] = 1;
      low[u] = min(low[u], low[v]);
    } else if (v != p)
      low[u] = min(low[u], num[v]);
  }
}
bool check(int u) {
  int sz = 0;
  vis[u] = 1;
  for (pair<int, int> x : g[u]) {
    int v = x.first, id = x.second;
    if (del[id]) continue;
    sz++;
    if (vis[v]) continue;
    if (!check(v)) return 0;
  }
  return sz == 2;
}
void mark(int u) {
  num[u] = 1;
  for (pair<int, int> x : g[u]) {
    int v = x.first, id = x.second;
    if (del[id]) continue;
    ans[id] = 1;
    if (num[v]) continue;
    mark(v);
  }
}
int main() {
  memset(num, -1, sizeof num);
  memset(vis, 0, sizeof vis);
  memset(low, 0, sizeof low);
  int n, m;
  scanf("%d %d", &n, &m);
  for (int i = 0; i < m; i++) {
    int a, b;
    scanf("%d %d", &a, &b);
    g[a].emplace_back(b, i);
    g[b].emplace_back(a, i);
  }
  for (int i = 1; i <= n; i++)
    if (num[i] == -1) dfs(i, i);
  memset(vis, 0, sizeof vis);
  memset(num, 0, sizeof num);
  for (int i = 1; i <= n; i++)
    if (!vis[i]) {
      bool ok = check(i);
      if (ok) mark(i);
    }
  int sz = 0;
  for (int i = 0; i < m; i++) sz += ans[i];
  printf("%d\n", sz);
  for (int i = 0; i < m; i++)
    if (ans[i]) printf("%d ", i + 1);
  printf("\n");
}
