#include <cstdio>
#include <vector>
#include <cstring>
#define nmax 100005

using namespace std;

int n,m,viz[nmax],st[nmax],vf,nr;
vector<int> g1[nmax],g2[nmax],sol[nmax];

void citire()
{
    int x,y;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        g1[x].push_back(y);
        g2[y].push_back(x);
    }
}

void dfs1(int k)
{
    viz[k]=1;
    for(vector<int>::iterator ii=g1[k].begin();ii!=g1[k].end();++ii)
        if(viz[*ii]==0)
            dfs1(*ii);
    st[++vf]=k;
}

void dfs2(int k)
{
    viz[k]=1;
    sol[nr].push_back(k);
    for(vector<int>::iterator ii=g2[k].begin();ii!=g2[k].end();++ii)
        if(viz[*ii]==0)
            dfs2(*ii);
}

void rezolv()
{
    for(int i=1;i<=n;i++)
        if(viz[i]==0)
            dfs1(i);
    memset(viz,0,sizeof(viz));
    for(int i=vf;i>=1;i--)
        if(viz[st[i]]==0)
            ++nr,dfs2(st[i]);
}

void afisare()
{
    printf("%d\n",nr);
    for(int i=1;i<=nr;i++)
    {
        for(vector<int>::iterator ii=sol[i].begin();ii!=sol[i].end();++ii)
            printf("%d ",*ii);
        printf("\n");
    }
}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    rezolv();
    afisare();
    return 0;
}