#include <bits/stdc++.h>

using namespace std;

const int NMAX = 1e5;

vector <int> edges[NMAX + 1];
vector <int> edgesT[NMAX + 1];

int viz[NMAX + 1];

vector <int> order;
vector <int> comp;

void dfs1( int node ) {
    viz[node] = true;
    for ( auto vec : edges[node] ) {
        if ( !viz[vec] ) dfs1( vec );
    }
    order.push_back( node );
}


void dfs2( int node ) {
    viz[node] = true;
    for ( auto vec : edges[node] ) {
        if ( !viz[vec] ) dfs2( vec );
    }
    comp.push_back( node );
}
int main() {
    ifstream fin( "ctc.in" );
    ofstream fout( "ctc.out" );
    int n, m;
    fin >> n >> m;
    for ( int i = 1, a, b; i <= m; i ++ ) {
        fin >> a >> b;
        edges[a].push_back( b );
        edgesT[b].push_back( a );
    }

    for ( int i = 1; i <= n; i ++ ) {
        if ( !viz[i] ) {
            dfs1( i );
        }
    }
    for ( int i = 1; i <= n; i ++ ) viz[i] = false;
    reverse( order.begin(), order.end() );

    vector <vector<int>> comps;
    for ( auto x : order ) {
        if ( !viz[x] ) {
            dfs2( x );
            comps.push_back( comp );
            comp.clear();
        }
    }
    fout << comps.size() << '\n';
    for ( auto c : comps ) {
        for ( auto x : c ) fout << x << ' ';
        fout << '\n';
    }
    return 0;
}