#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <stdio.h>
#include <ctype.h>
#define nrmax 100001
using namespace std;


class InParser {
private:
    FILE *fin;
    char *buff;
    int sp;

    char read_ch() {
        ++sp;
        if (sp == 4096) {
            sp = 0;
            fread(buff, 1, 4096, fin);
        }
        return buff[sp];
    }

public:
    InParser(const char* nume) {
        fin = fopen(nume, "r");
        buff = new char[4096]();
        sp = 4095;
    }

    InParser& operator >> (int &n) {
        char c;
        while (!isdigit(c = read_ch()) && c != '-');
        int sgn = 1;
        if (c == '-') {
            n = 0;
            sgn = -1;
        } else {
            n = c - '0';
        }
        while (isdigit(c = read_ch())) {
            n = 10 * n + c - '0';
        }
        n *= sgn;
        return *this;
    }

    InParser& operator >> (long long &n) {
        char c;
        n = 0;
        while (!isdigit(c = read_ch()) && c != '-');
        long long sgn = 1;
        if (c == '-') {
            n = 0;
            sgn = -1;
        } else {
            n = c - '0';
        }
        while (isdigit(c = read_ch())) {
            n = 10 * n + c - '0';
        }
        n *= sgn;
        return *this;
    }
};
InParser f("ctc.in");
ofstream g("ctc.out");

bool used[nrmax];
int st[nrmax];
int n , m , x, y , k , nr;
vector < int > G[nrmax];
vector < int > T[nrmax];
vector < int > ::iterator j;
vector < int > sol[nrmax];

void dfs ( int i )
{
    used[i] = 1;
    for (vector < int > ::iterator j = G[i].begin(); j != G[i].end(); j++)
    {
        if ( !used[ (*j) ] )
            dfs( (*j) );
    }
    st[++k] = i;
}

void dfsT ( int i )
{
    sol[nr].push_back(i);
    used[i] = 1;
    for (vector < int > ::iterator  j = T[i].begin() ; j != T[i].end(); j++ )
    {
        if ( !used [ (*j) ] )
            dfsT ( (*j) ) ;
    }
}

int main()
{
    f >> n >> m;
    for ( ; m-- ; )
    {
        f >> x >> y;
        G[x].push_back(y);
        T[y].push_back(x);
    }
    for ( int i = 1; i <= n ; i++ )
    {
        if ( !used[i] ) dfs(i);
    }
    memset(used,false,sizeof used);

    for ( int i = k ; i >= 1; i-- )
    {
        if ( !used[ st[i] ] )
        {
            nr++;
            dfsT(st[i]);
        }
    }
    g << nr << "\n" ;
    for ( int i = 1; i <= nr;  i++ )
    {
        for ( vector < int > ::iterator j = sol[i].begin(); j != sol[i].end(); j++ )
            g << (*j) << " " ;
        g << "\n" ;
    }
    return 0;
}