#include <stdio.h>
#include <vector>
#include <algorithm>
#define max 100010
using namespace std;
vector<int> g[max],comp[max];
int n,m,S[max],tops,B[2*max],I[max],topb,c,i,j;
int min(int a,int b){ if (a>b) return b; return a;}
void dfs(int v)//gabow
{
    S[++tops]=v; I[v]=tops;
    if(I[v]>1) B[++topb]=I[v];
    for(int i=0; i<g[v].size(); i++)
     if(I[g[v][i]]==0) { B[++topb]=I[v]; dfs(g[v][i]); }
     else while(I[v]>1 && I[g[v][i]]<B[topb-1]) topb-=2;
    if(I[v]==1) I[S[tops--]]=c;
    else
    if(I[v]==B[topb])
    {
        topb-=2;
        c++;
        while(I[v]<=tops)  I[S[tops--]]=c;
    }
}
int main()
{
    freopen("biconex.in","r",stdin);
    freopen("biconex.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(; m>0; m--)
    {
        scanf("%d%d",&i,&j);
        g[i].push_back(j);
        g[j].push_back(i);
    }
    c=n;
    for(i=1; i<=n; i++)
     if(I[i]==0) dfs(i);
    printf("%d\n",c-n);

   for(i=1; i<=n; i++)
    {
        for(j=0; j<g[i].size(); j++)
        {
            comp[min(I[i],I[g[i][j]])-n].push_back(i);
            comp[min(I[i],I[g[i][j]])-n].push_back(g[i][j]);
        }
    }
    for(i=1; i<=c-n; i++)
    {
       sort(comp[i].begin(),comp[i].end());
       comp[i].erase(unique(comp[i].begin(),comp[i].end()), comp[i].end());
        for(j=0; j<comp[i].size(); j++)
         printf("%d ",comp[i][j]);
        printf("\n");
    }

    return 0;
}