#include <fstream>
#include <queue>
#define NMAX 5005

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int M[NMAX][NMAX], n, m, result, visited[NMAX];

void Floyd_Warshall()
{
    int k, i, j;
    for(k = 1 ; k <= n; k++)
        for(i = 1; i <= n; i++)
            for(j = 1; j <= n; j++)
            if(M[i][k] == 1 && M[k][j] == 1 && i != j)
            M[i][j] = 1;
}

void BFS(int x)
{
    queue <int> Q;
    int i, v;
    Q.push(x);
    visited[x] = result;
    while(!Q.empty())
    {
        v = Q.front();
        Q.pop();
        for(i = 1; i <= n; i++)
            if(visited[i] == 0 && M[i][v] == 1 && M[v][i] == 1)
            {
                Q.push(i);
                visited[i] = result;
            }
    }
}
int main()
{
    int i, j, x, y;
    fin >> n >> m;
    for(i = 1; i <= m; i++)
    {
        fin >> x >> y;
        M[x][y] = 1;
    }
    Floyd_Warshall();
    for(i = 1; i <= n; i++)
        if(visited[i] == 0)
        {
            ++result;
            BFS(i);
        }
    fout << result << '\n';
    for(i = 1; i <= result; i++)
    {
        for(j = 1; j <= n; j++)
            if(visited[j] == i)
                fout << j << ' ';
        fout << '\n';
    }
    return 0;
}