#include <fstream>
#include <vector>
#define DIM 100001
#include <cstring>

using namespace std;

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

vector<int>L[DIM];
vector<int>Lt[DIM];
int n,m,i,j,x,y;
bool viz[DIM];
int top[DIM],nr;
vector<int>ct[DIM];
void dfs(int x)
{
    viz[x]=1;
    for(int i=0;i<L[x].size();i++)
    {
        int y=L[x][i];
        if(!viz[y])
            dfs(y);
    }
    top[++nr]=x;
}
int nrc;
void dfs2(int x)
{
    viz[x]=1;
    ct[nrc].push_back(x);
    for(int i=0;i<Lt[x].size();i++)
    {
        int y=Lt[x][i];
        if(!viz[y])
            dfs2(y);
    }
}
int main()
{
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>x>>y;
        L[x].push_back(y);
        Lt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(!viz[i])
            dfs(i);
    }
    memset(viz,0,sizeof(viz));
    for(i=n;i>=1;i--)
        if(viz[top[i]]==0)
        {
            nrc++;
            dfs2(top[i]);
        }
    fout<<nrc<<'\n';
    for(i=1;i<=nrc;i++)
    {
        for(j=0;j<ct[i].size();j++)
            fout<<ct[i][j]<<" ";
        fout<<'\n';
    }
    return 0;
}