#include <bits/stdc++.h>   using namespace std;   const double eps = 1e-10;   const double Pi = 3.1415926535897932;   const int dir[4][2] = {-1, 0, 0, -1, 1, 0, 0, 1};   const int maxn = 1e4 + 5;   struct EDGE {     int a, b;     int A, B;   } edge[maxn];   int n, m;   int last[maxn];   vector<int> G[maxn], tree[maxn];   int d[maxn];   int A[maxn], B[maxn];   bool vis[maxn];   vector<int> ans;   int in[maxn];   void dfs_tree(int a, int fa) {     vis[a] = true;     for (int i = 0; i < G[a].size(); i++) {       int p = G[a][i];       if (p == last[a]) continue;       int b = edge[p].a ^ edge[p].b ^ a;       if (!vis[b]) {         tree[a].push_back(p);         in[p] = true;         d[b] = d[a] + 1;         last[b] = p;         dfs_tree(b, a);       } else if (d[a] > d[b]) {         if (d[a] - d[b] + 1 & 1) {           ans.push_back(p);           B[a]++;           B[b]--;         } else {           A[a]++;           A[b]--;         }       }     }   }   void dfs(int a) {     vis[a] = true;     for (int i = 0; i < tree[a].size(); i++) {       int p = tree[a][i];       int b = edge[p].a ^ edge[p].b ^ a;       if (!vis[b]) dfs(b);       A[a] += A[b];       B[a] += B[b];     }     edge[last[a]].A = A[a];     edge[last[a]].B = B[a];   }   int main() {     scanf( %d%d , &n, &m);     for (int i = 1; i <= m; i++) {       int a, b;       scanf( %d%d , &a, &b);       edge[i] = EDGE{a, b};       G[a].push_back(i);       G[b].push_back(i);     }     for (int i = 1; i <= n; i++) {       if (!vis[i]) dfs_tree(i, -1);     }     memset(vis, false, sizeof(vis));     for (int i = 1; i <= n; i++) {       if (!vis[i]) dfs(i);     }     if (ans.size() == 0) {       for (int i = 1; i <= m; i++) ans.push_back(i);     } else if (ans.size() == 1) {       for (int i = 1; i <= m; i++)         if (in[i]) {           if (edge[i].A == 0 && edge[i].B) ans.push_back(i);         }     } else {       int t = ans.size();       ans.clear();       for (int i = 1; i <= m; i++)         if (in[i]) {           if (edge[i].B) {             if (edge[i].B == t && edge[i].A == 0) ans.push_back(i);           }         }     }     sort(ans.begin(), ans.end());     printf( %d n , ans.size());     for (int i = 0; i < ans.size(); i++)       printf( %d , ans[i]), putchar(i == ans.size() - 1 ?   n  :    );     return 0;   }   