#include<bits/stdc++.h>
 
using namespace std;
ifstream f("biconex.in");
ofstream g("biconex.out");
 
vector<int> visited,adjList[100001],low,id;
int temp=0,cnt=0;
vector<vector<int>> res;
void DFS(int x, int parent){
    int i;
    id[x]=temp;
    low[x]=temp;
    temp++;
 
    for(i=0;i<adjList[x].size();++i){
        if(parent!=adjList[x][i]){
            if(visited[adjList[x][i]]==0){
                visited[adjList[x][i]]++;
                DFS(adjList[x][i],x);
 
                low[x]=min(low[x],low[adjList[x][i]]);
 
                if(id[x]<low[adjList[x][i]]){
                    cnt++;
                    res.push_back({x,adjList[x][i]});
                }
                   
            }
            else{
                low[x]=min(low[x],id[adjList[x][i]]);
 
            }
        }
    }
 
}
 
int main(){
    int i;
 
    int n,m,a,b;
    f>>n>>m;
 
    for(i=0;i<n;++i){
        visited.push_back(0);
        id.push_back(0);
        low.push_back(0);
    }
 
    for(i=0;i<m;++i){
        f>>a>>b;
        adjList[a-1].push_back(b-1);
        adjList[b-1].push_back(a-1);
 
    }
 
    for(i=0;i<n;++i){
        if(visited[i]==0)
            {
                visited[i]=1;
                DFS(i,-1);
            }
    }
    visited[0]++;
    DFS(1,-1);
 
    unordered_map<int,vector<int>>umap;
 
    for(i=0;i<low.size();++i){
        umap[low[i]].push_back(i+1);
    }
 
    int j;
 
    
    vector<int> aux;
    for(auto x:umap){
        if(x.second.size()>1){
            cnt++;
            for(j=0;j<x.second.size();++j){
                aux.push_back(x.second[j]);
                cout<<x.second[j]<<' ';
            }
            res.push_back(aux);
            aux.clear();
        }
    }
    g<<cnt<<'\n';
    for(i=0;i<res.size();++i){
        for(j=0;j<res[i].size();++j){
            g<<res[i][j]+1<<' ';
        }
        g<<'\n';
    }
    return 0;
}