#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

const int NMAX = 1e5;

vector <int> edges[NMAX + 1];
vector <int> inv[NMAX + 1];
vector <int> ctc[NMAX];

bool viz[NMAX + 1];
int rev[NMAX], j;

void dfs( int node ) {

    viz[node] = true;

    for ( auto& i : edges[node] ) {
        if ( !viz[i] ) {
            dfs( i );
        }
    }
    rev[j++] = node;
}
void reset() {
    for ( int i = 0; i <= NMAX; i ++ ) {
        viz[i] = false;
    }
}
void dfs2( int node ) {
    ctc[j].push_back( node );
    viz[node] = true;

    for ( auto& i : inv[node] ) {
        if ( !viz[i] ) {
            dfs2( i );
        }
    }
}
int main() {
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    int n, m, i, a, b;
    fin >> n >> m;
    for ( i = 0; i < m; i ++ ) {
        fin >> a >> b;
        edges[a].push_back( b );
        inv[b].push_back( a );
    }

    for ( i = 1; i <= n; i ++ ) {
        if ( !viz[i] )
            dfs( i );
    }
    reset();
    j = 0;
    for ( i = n - 1; i >= 0; i -- ) {
        if ( !viz[rev[i]] ) {
            dfs2( rev[i] );
            j ++;
        }
    }
    fout << j << '\n';
    for ( i = 0; i < j; i ++ ) {
        for ( int x = 0; x < ctc[i].size(); x ++ ) {
            fout << ctc[i][x] << ' ';
        }
        fout << '\n';
    }
    return 0;
}