#include <bits/stdc++.h>

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector<int> A[100005] ,B[100005];
int n,m;
int viz1[100005];
int viz2[100005];
stack<int> S;
int ctc;
void Citire()
{
    int x,y,i,j;
    fin>>n>>m;
    for(i=1;i<=m; ++i)
    {
        fin>>x>>y;
        A[x].push_back(y);
        B[y].push_back(x);
    }
}

void DFS(int x)
{
    viz1[x]=1;
    for(int i=0; i< A[x].size(); ++i)
        if(viz1[ A[x][i] ] != 1)
            DFS( A[x][i] );
    S.push(x);
}

void DFS2(int x)
{
    viz2[x]=ctc;
    for(int i=0; i< B[x].size(); ++i)
        if(viz2[B[x][i]]==0)
            DFS2(B[x][i]);
}

void Do()
{
    int i,j,x;
    for(i=1; i<=n; ++i)
        if(viz1[i]!=1)
            DFS(i);
    while(!S.empty())
    {
        x=S.top();
        if(viz2[x]==0)
        {
            ctc++;
            DFS2(x);
        }
        S.pop();
    }
    fout<<ctc<<"\n";
    for(i=1; i<=ctc; ++i)
    {
        for(j=1;j<=n;++j)
            if(viz2[j]==i)
                fout<<j<<" ";
        fout<<"\n";
    }
}
int main()
{
    Citire();
    Do();
    return 0;
}