#include<stdio.h>
#include<stdlib.h>
int p,u,n,m,i,a[200002],b[200002],w[100001],*g[100001],c[100001],r,d[100001],f[100001];
char q[200002];
void P(int i) {
c[i]=2,q[++p]=i+'0';
for(int j=w[i]-1;j>=0;j--)
if(c[g[i][j]]==1)
P(g[i][j]);
}
void E(int i) {
d[i]=f[i]=u++,c[i]=1;
for(int j=w[i]-1;j>=0;j--)
if(!c[g[i][j]]) {
E(g[i][j]);
if(f[i]>f[g[i][j]])
f[i]=f[g[i][j]];
if(d[i]<=f[g[i][j]])
c[i]=2,q[++p]=i+'0',P(g[i][j]),c[i]=1,q[++p]='\n',r++;
}
else if(f[i]>d[g[i][j]])
f[i]=d[g[i][j]];
}
int main() {
freopen("biconex.in","r",stdin),freopen("biconex.out","w",stdout),scanf("%d%d",&n,&m);
for(i=1;i<=m;i++)
scanf("%d%d",&a[i],&b[i]),w[a[i]]++,w[b[i]]++;
for(i=1;i<=n;w[i++]=0)
g[i]=(int*)malloc(w[i]*sizeof(int));
for(i=1;i<=m;i++)
g[a[i]][w[a[i]]++]=b[i],g[b[i]][w[b[i]]++]=a[i];
for(i=1;i<=n;i++)
if(!c[i])
if(w[i])
E(i);
else
c[i]=2,q[++p]=i+'0',q[++p]='\n',r++;
printf("%d\n",r);
for(p--;p;p--)
printf("%c ",q[p]);
}