#include <bits/stdc++.h>
using namespace std;

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

const int M = 100001;

vector <int> pred[M], succ[M], cc[M];

long long n, m, stop[M], k, sol;

bool viz1[M], viz2[M];

void read()
{
    int i, x, y;
    fin >> n >> m;

    for(i = 1; i <= m; i++)
    {
        fin >> x >> y;
        succ[x].push_back(y);
        pred[y].push_back(x);
    }
}

void dfs_topologic(int nod)
{
    int i;
    viz1[nod] = true;

    for(i = 0; i < succ[nod].size(); i++)
    {
        int y = succ[nod][i];

        if(!viz1[y]) dfs_topologic(y);
    }

    stop[++k] = nod;
}

void dfs2(int nod)
{
    int i;
    viz2[nod] = true;
    cc[sol].push_back(nod);

    for(i = 0; i < pred[nod].size(); i++)
    {
        int y = pred[nod][i];

        if(!viz2[y]) dfs2(y);
    }
}

int main()
{
    read();
    int i, j;

    for(i = 1; i <= n; i++)
    {
        if(!viz1[i]) dfs_topologic(i);
    }

    for(i = n; i > 0; i--)
    {
        if(!viz2[stop[i]])
        {
            sol++;
            dfs2(stop[i]);
        }
    }
    fout << sol << '\n';

    for(i = 1; i <= sol; i++)
    {
        for(j = 0; j < cc[i].size(); j++)
        {
            fout << cc[i][j] << ' ';
        }
        fout << "\n";
    }
    return 0;
}