#include <fstream>
#include <stack>
#include <vector>
#define NMAX 100000

using namespace std;
ifstream fi("ctc.in");
ofstream fo("ctc.out");
int n, m, nrcomp;
int VIZ[NMAX+5];
vector <int> G[NMAX+5], GT[NMAX+5], SOL[NMAX+5];
stack <int> post;

void citire(void)
{
    int x, y;
    fi>>n>>m;
    for(int i=1; i<=m; i++)
    {
        fi>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void dfsPost(int nod)
{
    VIZ[nod]=1;
    for(auto vec:GT[nod])
        if(!VIZ[vec])
            dfsPost(vec);
    post.push(nod);
}

void dfsComp(int nod)
{
    VIZ[nod]=0;
    SOL[nrcomp].push_back(nod);
    for(auto vec:G[nod])
        if(VIZ[vec])
            dfsComp(vec);
}

void afisare(void)
{
    fo<<nrcomp<<"\n";
    for(int i=1; i<=nrcomp; i++)
    {
        for(int j=0; j<SOL[i].size(); j++)
            fo<<SOL[i][j]<<" ";
        fo<<"\n";
    }
}

int main()
{
    citire();
    for(int i=1; i<=n; i++)
        if(!VIZ[i])
            dfsPost(i);
    while(!post.empty())
    {
        if(VIZ[post.top()])
        {
            nrcomp++;
            dfsComp(post.top());
        }
        post.pop();
    }
    afisare();
    fi.close();
    fo.close();
    return 0;
}