#include <stdio.h>
#include <vector>
#include <cstring>
#include <deque>
using namespace std;
FILE *f,*g;
vector <int> graf[100010],graft[100010],ctc[100010];
deque <int> coada;
int used[100010];
int N,M;
void Read()
{
    int i,X,Y;
    fscanf(f,"%d %d",&N,&M);
    for(i=1;i<=M;++i)
    {
        fscanf(f,"%d %d",&X,&Y);
        graf[X].push_back(Y);graft[Y].push_back(X);
    }
}
void DFS(int Node)
{
    int i,t,vecin;
    t=graf[Node].size();
    used[Node]=1;
    for(i=0;i<t;++i)
    {
        vecin=graf[Node][i];
        if(!used[vecin])DFS(vecin);
    }
    coada.push_back(Node);
}
int Nr;
void SFD(int Node)
{
    int i,t,vecin;
    t=graft[Node].size();
    used[Node]=1;
    for(i=0;i<t;++i)
    {
        vecin=graft[Node][i];
        if(!used[vecin])SFD(vecin);
    }
    ctc[Nr].push_back(Node);
}
void Solve()
{
    int i,Node;
    for(i=1;i<=N;++i)
        if(!used[i])DFS(i);
    memset(used,0,sizeof(used));
    while(!coada.empty())
    {
        Node=coada.back();
        coada.pop_back();
        if(!used[Node])
        {
            ++Nr;
            SFD(Node);
        }
    }
}
void Displaying()
{
    int i,j;
    fprintf(g,"%d\n",Nr);
    for(i=1;i<=Nr;++i,fprintf(g,"\n"))
        for(j=0;j<ctc[i].size();++j)fprintf(g,"%d ",ctc[i][j]);
}
int main()
{
    f=fopen("ctc.in","r");
    g=fopen("ctc.out","w");
    Read();Solve();Displaying();
    fclose(f);
    fclose(g);
    return 0;
}