#include <iostream>
#include <cstdio>
#include <vector>

using namespace std;

vector <int> L[100002], LT[100002];
vector <int> ctc[100002],idx;
int viz[100002];
int n,m,nr,nrctc;

void citire()
{
    freopen("ctc.in","r",stdin);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        int x,y; scanf("%d%d",&x,&y);
        L[x].push_back(y);
        LT[y].push_back(x);
    }
}

void DFS(int v)
{
    viz[v]=1;
    for(vector <int> ::iterator it=L[v].begin();it!=L[v].end();it++)
       if(!viz[*it])
            DFS(*it);
    idx.push_back(v);

}

void DFST(int v)
{
    viz[v]=0;ctc[nrctc].push_back(v);
    for(vector <int>::iterator it=LT[v].begin();it!=LT[v].end();it++)
       if(viz[*it])
            DFST(*it);
}


int main()
{
    citire();
    for(int i=1;i<=n;i++)
        if(!viz[i])
            DFS(i);
    for(int i=idx.size()-1;i>=0;i--)
        if(viz[idx[i]])
             {
                 nrctc++;
                 DFST(idx[i]);

             }
    freopen("ctc.out","w",stdout);
    printf("%d\n",nrctc);
    for(int i=1;i<=nrctc;i++)
    {

        for (vector<int>::iterator it=ctc[i].begin(); it!=ctc[i].end(); it++)
             printf("%d ",*it);
        printf("\n");
    }
    return 0;
}