#include <bits/stdc++.h>

std :: ifstream in ("ctc.in");

std :: ofstream out ("ctc.out");

const int NMAX = 1e5 + 5;

int n;

int m;

int x;

int y;

int cnt;

std :: vector <int> v[NMAX];

std :: vector <int> tout;

std :: bitset <NMAX> visited;

std :: vector <int> t[NMAX];

std :: vector <int> comp;

std :: stack <std :: vector <int>> s;

void dfs(int nod)
{
    for(int i : v[nod])
    {
        if(visited[i] == false)
        {
            visited[i] = true;

            dfs(i);
        }
    }

    tout.push_back(nod);
}

void dfs1(int nod)
{
    comp.push_back(nod);

    for(int i : t[nod])
    {
        if(visited[i] == false)
        {
            visited[i] = true;

            dfs1(i);
        }
    }
}

int main()
{

    in >> n >> m;

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

        v[x].push_back(y);

        t[y].push_back(x);
    }

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

            dfs(i);
        }
    }

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

    visited &= 0;

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

            visited[i] = true;

            dfs1(i);

            s.push(comp);

            comp.clear();
        }
    }

    out << cnt << '\n';

    while(!s.empty())
    {
        for(int i : s.top())
        {
            out << i << " ";
        }

        out << '\n';

        s.pop();
    }

    return 0;
}