#include <fstream>
#include <stack>
#include <vector>

using namespace std;

class Graph {
private:
    int _nodes, _edges;
    vector<vector<int>> _adj_list;
    /*here for convenience*/
    int _crt_index = 1;
    stack<int> _comp_stack;
    vector<vector<int>> _components;
    vector<bool> _onStack;
    vector<int> _index;
    vector<int> _lowlink;

    void dfs(const int start){
        _index[start] = _crt_index++;
        _lowlink[start] = _index[start];
        _comp_stack.push(start);
        _onStack[start] = true;
        for (const auto node : _adj_list[start]) {
                if (!_index[node]) {
                    dfs(node);
				}
                _lowlink[start] = min(_lowlink[start], _lowlink[node]);
        }
        if(_lowlink[start]==_index[start]){
            vector<int> component;
            while (_comp_stack.top() != start){
                const int node = _comp_stack.top();
                _comp_stack.pop();
                _onStack[node] = false;
            	component.push_back(node);

            }
            component.push_back(start);
            _onStack[start] = false;
            _comp_stack.pop();
            _components.push_back(move(component));
        }
    }

public:
    Graph(int nodes, int edges, vector<vector<int>> adj_list) :
        _nodes(nodes),
        _edges(edges),
        _adj_list(std::move(adj_list)) {}

    vector<vector<int>> stronglyConnected(){
        _crt_index = 1;
        _onStack = vector<bool>(_nodes+1,false);
        _index = vector<int>(_nodes + 1, 0);
        _lowlink = vector<int>(_nodes + 1, 0);

        for(int node = 1;node<=_nodes;++node){
	        if(!_index[node]){
                dfs(node);
	        }
        }
        return _components;
    }
};

int main(){
    ifstream in("ctc.in");
    int nodes, edges;
    in >> nodes >> edges;
    vector<vector<int>> adj_list(nodes+1);
    for(int i=0; i<edges; ++i)
    {
        int node1, node2;
        in >> node1 >> node2;
        adj_list[node1].push_back(node2);
    }
    in.close();
    ofstream out("ctc.out");
    Graph g(nodes, edges, adj_list);
    auto stronglyConnected = g.stronglyConnected();
    out << stronglyConnected.size()<<"\n";
    for(auto comp : stronglyConnected){
	    for(auto node : comp){
            out << node << " ";
	    }
        out << "\n";
    }

}