#include <iostream>
#include <fstream>
#include <vector>
#include <stack>

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

const int N=100000;

std::vector<int> v[N+1];
std::vector<int> t[N+1];
std::vector<int> rez[N+1];

int n, m;

std::stack<int> q;
bool tp[N+1];
void sort_tp(int i)
{
    tp[i]=true;

    for(int copil : v[i])
    {
        if(!tp[copil])
        {
            sort_tp(copil);
        }
    }

    q.push(i);
}

bool transpus[N+1];
void Dfs_transpus(int i, int nr)
{
    transpus[i]=true;

    for(int copil : t[i])
    {
        if(!transpus[copil])
        {
            Dfs_transpus(copil, nr);
        }
    }

    rez[nr].push_back(i);
}

int main()
{
    int x, y;

    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(!tp[i])
        {
            sort_tp(i);
        }
    }

    int nr=0;
    while(!q.empty())
    {
        if(!transpus[q.top()])
        {
            nr++;
            Dfs_transpus(q.top(), nr);
        }

        q.pop();
    }

    out<<nr<<"\n";
    for(int i=1; i<=n; i++)
    {
        for(int copil : rez[i])
        {
            out<<copil<<" ";
        }
        out<<"\n";
    }
}