#include <vector>
#include <fstream>

using namespace std;
#define nmax 100000

vector <bool> viz;
ifstream cin("ctc.in");
ofstream cout("ctc.out");

void dfs( int node, vector<vector<int>>& edges, vector <int>& add_to ) {
    viz[node] = true;
    for( auto new_node : edges[node] ) {
        if( !viz[new_node] )
            dfs( new_node, edges, add_to );
    }
    add_to.push_back( node );
}

void solve() {
    int n, m, x, y;
    cin >> n >> m;
    vector <vector <int> > edges(n);
    vector <vector <int> > rev_edges(n);
    vector <vector <int>> ctc;
    vector <int> st;
    viz.resize(n);

    for( int i = 0; i < m; i++ ) {
        cin >> x >> y; x--; y--;
        edges[x].push_back( y );
        rev_edges[y].push_back( x );
    }

    for (int node = 0; node < n; node++) {
        if( !viz[node] ) {
            dfs(node, edges, st);
        }
    }

    viz.clear();
    viz.resize(n);
    for (int i = st.size() - 1; i >= 0; i--) {
        if (viz[st[i]] == 0) {
            ctc.push_back(vector<int>());
            dfs(st[i], rev_edges, ctc.back());
        }
    }

    cout << ctc.size() << "\n";
    for ( auto comp : ctc ) {
        for (auto node : comp) {
            cout << node + 1 << " ";
        }
        cout << "\n";
    }

}

int main() {
    solve();
    return 0;
}