#include <fstream>
#include <vector>
#define nmax 100002
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector <int> gr[nmax];
vector <int> g[nmax];
vector <int> solutie[nmax];

int viz[nmax],post[nmax],nn=0,contor=0;

void dfs(int nod)
{
    viz[nod]=1;
    for(int i=0;i<gr[nod].size();i++)
    {
        if(viz[gr[nod][i]]==0)
        {
            viz[gr[nod][i]]=1;
            dfs(gr[nod][i]);
        }
    }
    post[++nn]=nod;
}

void dfsr(int nod)
{
    solutie[contor].push_back(nod);
    viz[nod]=0;
    for(int i=0;i<g[nod].size();i++)
    {
        if(viz[g[nod][i]])
        {
            viz[g[nod][i]]=0;
            dfsr(g[nod][i]);
        }
    }
}

int main()
{
    int n,m,x,y;
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        gr[x].push_back(y);
        g[y].push_back(x);
    }
    for(int i=1;i<=n;i++)
        if(!viz[i])
            dfs(i);
    for(int i=nn;i>=1;i--)
    {
        if(viz[post[i]])
        {
            contor++;
            dfsr(post[i]);
        }
    }
    fout<<contor<<"\n";
    for(int i=1;i<=contor;i++)
    {
        for(int j=0;j<solutie[i].size();j++)
        {
            fout<<solutie[i][j]<<" ";
        }
        fout<<"\n";
    }
    return 0;
}