#include <bits/stdc++.h>

using namespace std;

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

#define int long long

const int NMAX = 1e5 + 5;

int n, m;

vector <int> v[NMAX], t[NMAX];

vector <int> tout;

bitset <NMAX> visited;

vector<int> comp[NMAX];

int cnt;

void dfs2(int nod)
{
    comp[cnt].push_back(nod);

    visited[nod] = true;

    for(auto & i : t[nod])
    {
        if(visited[i]) continue;

        dfs2(i);
    }
}

void dfs(int nod)
{
    visited[nod] = true;

    for(auto & i : v[nod])
    {
        if(visited[i]) continue;

        dfs(i);
    }

    tout.push_back(nod);
}

int32_t main()
{

    //ios_base :: sync_with_stdio(false);
    //cin.tie(0);


    f >> n >> m;

    for(int i = 1; i <= m; i ++)
    {
        int x, y;
        f >> x >> y;

        v[x].push_back(y);
        t[y].push_back(x);
    }

    for(int i = 1; i <= n; i ++)
    {
        if(visited[i] == false)
        {
            dfs(i);
        }
    }

    reverse(tout.begin(), tout.end());

    visited &= 0;

    for(auto & i : tout)
    {
        if(visited[i] == false)
        {
            cnt ++;
            dfs2(i);
        }
    }

    g << cnt << '\n';

    for(int i = 1; i <= cnt; i ++)
    {
        for(auto & j : comp[i])
        {
            g << j << " ";
        }

        g << '\n';
    }

    return 0;
}