#include<cstdio>
#include<vector>
#include<cstring>
using namespace std;
int n,m,v[100001],viz[100001],x[100001],nr,num;
vector <int> l[100001],lt[100001];





void dfs(int u)
{
    vector<int>::iterator it;
    viz[u]=1;
    for(it=l[u].begin();it!=l[u].end();++it)
        if(viz[*it]==0)
            dfs(*it);
    v[++nr]=u;
}



void dfs2(int u)
{
    vector<int>::iterator it;
    viz[u]=1;
    for(it=lt[u].begin();it!=lt[u].end();++it)
        if(viz[*it]==0)
            dfs2(*it);
    x[u] = num;
}




int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    int i,j,u,w;
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;++i)
    {
        scanf("%d%d",&u,&w);
        l[u].push_back(w);
        lt[w].push_back(u);
    }
    for(i=1;i<=n;++i)
        if(!viz[i])
            dfs(i);
    num=0;
    memset(viz,0,sizeof(viz));
    for(i=n;i>=1;--i)
        if(viz[v[i]]==0)
        {
            ++num;
            dfs2(v[i]);
        }
    printf("%d\n",num);
    for(i=1;i<=num;++i)
    {
        for(j=1;j<=n;++j)
            if(x[j]==i)
                printf("%d ",j);
        printf("\n");
    }
    return 0;
}