#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int maxn=1000010;
int n,m,sum,ans,cnt;
int f[maxn],to[maxn<<1],next[maxn<<1],ont[maxn<<1],head[maxn],pa[maxn],pb[maxn],vis[maxn],dep[maxn];
int fa[20][maxn],Log[maxn],pc[maxn],s1[maxn],s0[maxn],from[maxn],ok[maxn];
int find(int x)
{return (f[x]==x)?x:(f[x]=find(f[x]));
}
inline void add(int a,int b)
{to[cnt]=b,next[cnt]=head[a],head[a]=cnt++;
}
void dfs1(int x)
{vis[x]=1;for(int i=head[x];i!=-1;i=next[i])    if(!vis[to[i]])ont[i]=1,fa[0][to[i]]=x,dep[to[i]]=dep[x]+1,from[to[i]]=(i>>1)+1,dfs1(to[i]);
}
inline int lca(int a,int b)
{if(dep[a]<dep[b])   swap(a,b);for(int i=Log[dep[a]-dep[b]];i>=0;i--)   if(dep[fa[i][a]]>=dep[b])   a=fa[i][a];if(a==b)  return a;for(int i=Log[dep[a]];i>=0;i--)   if(fa[i][a]!=fa[i][b]) a=fa[i][a],b=fa[i][b];return fa[0][a];
}
void dfs2(int x)
{for(int i=head[x];i!=-1;i=next[i])  if(ont[i])  dfs2(to[i]),s1[x]+=s1[to[i]],s0[x]+=s0[to[i]];
}
inline int rd()
{int ret=0,f=1;   char gc=getchar();while(gc<'0'||gc>'9')  {if(gc=='-')    f=-f;  gc=getchar();}while(gc>='0'&&gc<='9')  ret=ret*10+(gc^'0'),gc=getchar();return ret*f;
}
int main()
{n=rd(),m=rd();int i,j;memset(head,-1,sizeof(head));for(i=1;i<=n;i++)  f[i]=i;for(i=1;i<=m;i++){pa[i]=rd(),pb[i]=rd(),add(pa[i],pb[i]),add(pb[i],pa[i]);if(find(pa[i])!=find(pb[i]))    f[f[pa[i]]]=f[pb[i]];}for(i=1;i<=n;i++) if(!vis[i]) dep[i]=1,dfs1(i);for(i=2;i<=n;i++)  Log[i]=Log[i>>1]+1;for(j=1;(1<<j)<=n;j++)  for(i=1;i<=n;i++)    fa[j][i]=fa[j-1][fa[j-1][i]];for(i=1;i<=m;i++)  if(!ont[i*2-2]&&!ont[i*2-1]){pc[i]=lca(pa[i],pb[i]);if(!((dep[pa[i]]^dep[pb[i]])&1))   sum++,s1[pa[i]]++,s1[pb[i]]++,s1[pc[i]]-=2;else  s0[pa[i]]++,s0[pb[i]]++,s0[pc[i]]-=2;}for(i=1;i<=n;i++) if(dep[i]==1) dfs2(i);if(!sum){printf("%d\n",m);for(i=1;i<=m;i++)    printf("%d%c",i,i==m?'\n':' ');return 0;}if(sum==1)   for(i=1;i<=m;i++)    if(!ont[i*2-2]&&!ont[i*2-1]&&!((dep[pa[i]]^dep[pb[i]])&1))  ok[i]=1,ans++;for(i=1;i<=n;i++)   if(s1[i]==sum&&!s0[i])    ok[from[i]]=1,ans++;printf("%d\n",ans);for(i=1;i<=m;i++)    if(ok[i])   printf("%d%c",i,(--ans)?' ':'\n');return 0;
}//5 6 1 2 1 3 2 3 2 5 3 6 5 6