#include <bits/stdc++.h>
#define inf 1000000003

using namespace std;

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

vector<int> G[100001];
vector<int> compcon[100001];
int viz[100001], TSORT[100001], viz2[100001];
int n,m,k,l;

void dfs(int nod){
    viz[nod] = 1;
    for(auto vecin: G[nod]){
        if(!viz[vecin])
            dfs(vecin);
    }
    TSORT[++k] = nod;
}

void parcdfs(int nod,int comp){
    viz2[nod] = 1;
    compcon[comp].push_back(nod);
    for(auto vecin: G[nod]){
        if(!viz2[vecin]){
            parcdfs(vecin,comp);
        }
    }
}

int main(){
    int i,a,b;
    fin>>n>>m;
    for(i = 1; i <= m; i++){
        fin>>a>>b;
        G[a].push_back(b);
    }
    for(i = 1; i<= n; i++){
        if(!viz[i]){
            dfs(i);
        }
    }
    for(i = 1; i <= n; i++){
        if(!viz2[TSORT[i]]){
            l++;
            parcdfs(TSORT[i],l);
        }
    }
    fout<<l<<'\n';
    for(i = 1; i <= l; i++){
        for(auto nod: compcon[i]){
            fout<<nod<<' ';
        }
        fout<<'\n';
    }
    return 0;
}