#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cstring>

#define nrmax 100001
using namespace std;
class InputReader {
    public:
        InputReader() {}
        InputReader(const char *file_name) {
            input_file = fopen(file_name, "r");
            cursor = 0;
            fread(buffer, SIZE, 1, input_file);
        }
        inline InputReader &operator >>(int &n) {
            while(buffer[cursor] < '0' || buffer[cursor] > '9') {
                advance();
            }
            n = 0;
            while('0' <= buffer[cursor] && buffer[cursor] <= '9') {
                n = n * 10 + buffer[cursor] - '0';
                advance();
            }
            return *this;
        }
    private:
        FILE *input_file;
        static const int SIZE = 1 << 17;
        int cursor;
        char buffer[SIZE];
        inline void advance() {
            ++ cursor;
            if(cursor == SIZE) {
                cursor = 0;
                fread(buffer, SIZE, 1, input_file);
            }
        }
};
InputReader 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;
}