#include <bits/stdc++.h>

using namespace std;

const int NMAX = 100000;

bool viz[NMAX + 1];

void dfs( int node, const vector<vector <int>>& edges, vector <int>& order ) {
    viz[node] = true;
    for ( auto vec : edges[node] ) {
        if ( !viz[vec] ) {
            dfs( vec, edges, order );
        }
    }
    order.push_back( node );
}
int main() {
    ifstream fin( "ctc.in" );
    ofstream fout( "ctc.out" );
    int n, m;
    fin >> n >> m;
    vector<vector <int>> edges;
    vector<vector <int>> trans;
    edges.resize( n );
    trans.resize( n );
    for ( int i = 1, a, b; i <= m; i ++ ) {
        fin >> a >> b; a--; b--;
        edges[a].push_back( b );
        trans[b].push_back( a );
    }
    vector <int> order, useless;
    for ( int i = 0; i < n; i ++ ) {
        if ( !viz[i] ) {
            dfs( i, edges, order );
        }
    }
    for ( int i = 0; i < n; i ++ ) viz[i] = false;
    reverse( order.begin(), order.end() );
    vector <vector<int>> comps;
    for ( auto x : order ) {
        if ( !viz[x] ) {
            comps.push_back( {} );
            dfs( x, trans, comps[comps.size() - 1] );
        }
    }
    fout << comps.size() << '\n';
    for ( auto comp : comps ) {
        for ( auto node : comp ) {
            fout << node + 1 << ' ';
        }
        fout << '\n';
    }
    return 0;
}