#include<cstdio>

 #include<cstdlib>

 #include<algorithm>

 #include<cstring>

 #include<vector>

 #define pii pair<int,int>

 #define pb push_back

 #define mp make_pair

 #define ft first

 #define sc second

 #define MAXN 1000000+10

 using namespace std;

 int first[MAXN],edges[MAXN<<],nxt[MAXN<<],to[MAXN<<];

 int n,m,c=-;

 int b[MAXN],d[MAXN],tag[MAXN];

 int tmp,cnt,self_tmp;

 void insert(int x,int y,int e){

     nxt[++c]=first[x],first[x]=c,to[c]=y,edges[c]=e;

     nxt[++c]=first[y],first[y]=c,to[c]=x,edges[c]=e;

 }

 void init(){

     scanf("%d%d",&n,&m);

     int x,y;

     for(int i=;i<=m;i++){

         scanf("%d%d",&x,&y);

         if(x==y&&!self_tmp){self_tmp=i;continue;}

         if(x==y){self_tmp=-;continue;}

         insert(x,y,i);

     }

 }

 void dfs(int x,int fa){

     for(int e=first[x];e;e=nxt[e]){

         if(e==(fa^))continue;

         int &y=to[e];

         if(d[y]){

             if(d[x]<d[y])continue;

             if((d[x]-d[y]+)&){

                 tag[x]++,tag[y]--;

                 cnt++;tmp=edges[e];

             }

             else{

                 tag[x]--,tag[y]++;

             }

         }

         else{

             d[y]=d[x]+;

             dfs(y,e);

             tag[x]+=tag[y];

         }

     }

 }

 vector<int> ans;

 void find(int x){

     b[x]=;

     for(int e=first[x];e;e=nxt[e]){

         int &y=to[e];

         if(b[y])continue;

         if(tag[y]==cnt){

             ans.pb(edges[e]);

         }

         find(y);

     }

 }

 void solve(){

     if(-==self_tmp){printf("0\n");return;}

     for(int i=;i<=n;i++){

         if(!d[i])d[i]=,dfs(i,);

     }

     if(!cnt){

         if(self_tmp){printf("1\n%d\n",self_tmp);}

         else{printf("%d\n",m);for(int i=;i<m;i++)printf("%d ",i);printf("%d\n",m);}

         return;

     }

     if(self_tmp){printf("0\n");return;}

     for(int i=;i<=n;i++){

         if(!b[i])find(i);

     }

     if(cnt==)ans.pb(tmp);

     sort(ans.begin(),ans.end());

     printf("%d\n",ans.size());

     for(int i=;i<ans.size();i++){

         printf("%d",ans[i]);

         if(i==ans.size()-)printf("\n");

         else printf(" ");

     }

 }

 int main()

 {

 //  freopen("data.in","r",stdin);

 //  freopen("my.out","w",stdout);

     init();

     solve();

     return ;

 }