#include <bits/stdc++.h>
#define pii pair<int,int>
#define pb push_back
#define ll long long


using namespace std;

ifstream fin("biconex.in");
ofstream fout("biconex.out");

const int nmax=1e5;

vector<int>v[nmax+1];
vector<int>scc[nmax+1];

int d[nmax+1],low[nmax+1],timer,sccs;

stack<pii>stk;

void get_scc(pii e){
    sccs++;
    pii t;
    do{
        t=stk.top();
        stk.pop();
        scc[sccs].pb(t.first);
        scc[sccs].pb(t.second);
    }while(t!=e);
}

void dfs(int nod,int pr){
    low[nod]=d[nod]=++timer;
    for(int i:v[nod]){
        if(i==pr)
            continue;
        if(d[i])
            low[nod]=min(low[nod],d[i]);
        else{
            stk.push({nod,i});
            dfs(i,nod);
            low[nod]=min(low[nod],low[i]);
            if(low[i]>=d[nod])///art point
                get_scc({nod,i});
        }
    }
}

int main()
{
    int n,m;
    fin>>n>>m;
    while(m--){
        int st,dr;
        fin>>st>>dr;
        v[st].pb(dr);
    }
    dfs(1,0);
    fout<<sccs<<'\n';
    for(int i=1;i<=sccs;i++){
        sort(scc[i].begin(),scc[i].end());
        scc[i].erase(unique(scc[i].begin(),scc[i].end()),scc[i].end());
        for(int j:scc[i])
            fout<<j<<' ';
        fout<<'\n';
    }
    return 0;
}