#include<bits/stdc++.h>
using namespace std;

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

const int DIM = 1e5 + 5;

int low[DIM], niv[DIM], cod, N, M, K;
bool f[DIM];
stack<int> st;
vector<int> edge[DIM], ctc[DIM];

void dfs( int nod ){
    niv[nod] = low[nod] = ++cod;
    st.push( nod );
    f[nod] = true;
    for( int i = 0; i < edge[nod].size(); i++ ){
        int vec = edge[nod][i];
        if( f[vec] == true )
            low[nod] = min( low[nod], low[vec] );
        else{
            dfs( vec );
            low[nod] = min( low[nod], low[vec] );
        }
    }
    if( low[nod] == niv[nod] ){
        K++;
        while( !st.empty() && st.top() != nod ){
            ctc[K].push_back( st.top() );
            st.pop();
        }
        ctc[K].push_back( st.top() );
        st.pop();
    }
}

int main(){
    fin >> N >> M;
    for( int i = 1; i <= M; i++ ){
        int x, y; fin >> x >> y;
        edge[x].push_back( y );
    }

    for( int i = 1; i <= N; i++ ){
        if( niv[i] == 0 ){
            dfs( i );
        }
    }

    fout << K << "\n";
    for( int i = 1; i <= K; i++, fout << "\n" )
        for( int j = 0; j < ctc[i].size(); j++, fout << " " )
            fout << ctc[i][j];

    return 0;
}