#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <algorithm>

using namespace std;
const int maxn = 100;
bool visited[maxn];
vector<int> edges[maxn];
int intime[maxn];
int lowlink[maxn];
int n,m;
int ttime = 1;

set< pair<int,int> > bridges;
map< pair<int,int>,int > mmap;

void dfs(int v,int p)
{
   if(visited[v])return;
   visited[v]=true;
   intime[v]=ttime;
   lowlink[v]=ttime++;
   for(int i =0;i<edges[v].size();i++)
   {
       int child = edges[v][i];
       if(child == p)continue;
       if(visited[child])
       {
           lowlink[v] = min(lowlink[v],intime[child]);
       }
       else
       {
           dfs(child,v);
           lowlink[v] = min(lowlink[v],lowlink[child]);

           if(lowlink[v]<lowlink[child])
           {
               bridges.insert(make_pair(min(v,child),max(v,child)));
           }
       }
   }
}

int main()
{
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    cin>>n>>m;
   int i,j,k;
   for(i = 0;i<m;i++)
   {
       cin>>j>>k;
       edges[j].push_back(k);
       edges[k].push_back(j);
       mmap[make_pair(min(j,k),max(j,k))]= i+1;
   }
   for(i =1;i<=n;i++)
       if(!visited[i])
           dfs(i,-1);

   cout<<bridges.size()<<endl;
   i = 0;
vector<int> t;
   for(set< pair<int,int> >::iterator iter = bridges.begin();iter!=bridges.end();iter++)
   {
        t.push_back(mmap[(*iter)]);
   }
   sort(t.begin(),t.end());
    for(i = 0;i<t.size();i++)
    {
        cout<<t[i];
       if(i!=t.size()-1)cout<<endl;
    }
   return 0;
}