#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
#define MAX_N 100005

using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");

vector <int> G[MAX_N], GT[MAX_N], C[MAX_N/2];
int Stack[MAX_N], top, comp_conexe;
bitset <MAX_N> viz, vizt;

void dfs(int nod)
{
    viz[nod] = 1;
    for(int i = 0; i < G[nod].size(); i++)
        if(viz[G[nod][i]] == 0)
            dfs(G[nod][i]);
    Stack[++top] = nod;
}

void dfst(int nod)
{
    vizt[nod] = 1;
    for(int i = 0; i < GT[nod].size(); i++)
        if(vizt[GT[nod][i]] == 0)
            dfst(GT[nod][i]);
}

int main()
{
    int N, M, i, x, y;
    f >> N >> M;
    for(i = 1; i <= M; i++)
    {
        f >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
    for(i = 1; i <= N; i++)
        if(viz[i] == 0)
            dfs(i);
    while(top != 0)
    {
        int nod = Stack[top];
        dfst(nod);
        comp_conexe++;
        for(int j = 1; j <= top; j++)
            if(vizt[Stack[j]] == 1)
                {
                    C[comp_conexe].push_back(Stack[j]);
                    for(int k = j; k < top; k++)
                        Stack[k] = Stack[k+1];
                    j--;
                    top--;
                }
    }
    g<<comp_conexe<<endl;
    for(i = 1; i <= comp_conexe; i++)
    {
        for(int j = 0; j < C[i].size(); j++)
            g<<C[i][j]<<" ";
        g<<endl;
    }
    return 0;
}