#include <iostream>
#include <stdio.h>
#include <vector>
#include <stack>
#define NMax 100002
using namespace std;
vector<int> Graf[NMax],GrafTranspus[NMax],Sol[NMax];
stack<int> Stiva;
int N,M,x,y;
int Comp[NMax];
bool mark[NMax];
int ComponentaTareConexa;

void Read()
{
    freopen("ctc.in","r",stdin);
    scanf("%d%d",&N,&M);
    for(int i=1;i<=M;i++)
    {
        scanf("%d%d",&x,&y);
        Graf[x].push_back(y);
        GrafTranspus[y].push_back(x);
    }
}

void DFS1(int nod)
{
    mark[nod]=true;
    for(vector<int>::iterator it=Graf[nod].begin();it!=Graf[nod].end();it++)
        if(mark[*it]==false)
            DFS1(*it);

    Stiva.push(nod);
}

void DFSTranspus(int nod)
{
    Comp[nod]=ComponentaTareConexa;
    Sol[ComponentaTareConexa].push_back(nod);
    for(vector<int>::iterator it=GrafTranspus[nod].begin();it!=GrafTranspus[nod].end();it++)
        if(Comp[*it]==0)
            DFSTranspus(*it);
}

void Kosajaru()// =))))) Lool...Acum mi-am dat seama ca e defapt Kosaraju...
{
    for(int i=1;i<=N;i++)
        if(mark[i]==false)
        DFS1(i);

    while(Stiva.empty()==false)
    {
        if(Comp[Stiva.top()]==0)
        {
            ++ComponentaTareConexa;
            DFSTranspus(Stiva.top());
        }
        Stiva.pop();
    }
}

void Write()
{
    printf("%d\n",ComponentaTareConexa);
    for(int i=1;i<=ComponentaTareConexa;i++)
    {
        for(vector<int>::iterator it=Sol[i].begin();it!=Sol[i].end();it++)
            printf("%d ",*it);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    Read();
    Kosajaru();
    Write();
}