#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fcin("ctc.in");
ofstream fcout("ctc.out");

int conexe;
vector<vector<int>> AdjList, result;
vector<vector<int>> iAdjList;
vector<int> visited;
stack<int> stck;

void DFS_Transpus(int node) {
    visited[node] = 2;
    result[conexe].push_back(node);
    vector<int> nodeAdjList = iAdjList[node];
    for(auto i = nodeAdjList.begin(); i!=nodeAdjList.end(); i++)
        if(visited[*i] == 1)
            DFS_Transpus(*i);

}

void DFS(int node)
{
    visited[node] = 1;
    vector<int> nodeAdjList = AdjList[node];

    for(auto i = nodeAdjList.begin(); i!=nodeAdjList.end(); i++) {
        if(!visited[*i])
            DFS(*i);
    }
    stck.push(node);
}

int main()
{
    int n, m;
    fcin>>n>>m;

    AdjList.resize(n+1);
    iAdjList.resize(n+1);
    visited.resize(n+1);
    result.resize(n+1);

    // construim lista de adiacenta + lista de adiacenta pentru inversa
    for(int i=1; i<=m; i++)
    {
        int x, y;
        fcin>>x>>y;
        AdjList[x].push_back(y);
        iAdjList[y].push_back(x);
    }

    for(int i=1; i<=n; i++)
        if(!visited[i])
            DFS(i);

    while(!stck.empty()) {
        int node = stck.top();
        //cout << node << " ";
        if(visited[node] == 1) {
            conexe++;
            DFS_Transpus(node);
        }
        stck.pop();
    }
    fcout << conexe << endl;

    for(int i=1; i<=conexe; i++) 
    {
        for(int j = 0; j<result[i].size(); j++)
            fcout<<result[i][j] << " ";
        fcout<<endl;
    }
        

    return 0;
}