#include<vector>
#include<cstdio>
using namespace std;
vector<int> succ[100001], pred[100001], sol[100001];
int k,n,m,viz[100001],st[100001],nr_comp;
void citire()
{
    freopen("ctc.in","r",stdin);
    int x,y;
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        succ[x].push_back(y);
        pred[y].push_back(x);
    }
}
void DF_succ(int x)
{
    viz[x]=1;
    k++;//!!!
    st[k]=x;//!!!
    for(vector<int>::iterator it=succ[x].begin();it!=succ[x].end();++it)
        if(viz[*it]==0) DF_succ(*it);

}
void DF_pred(int x)
{
    viz[x]=1;
    sol[nr_comp].push_back(x); //!!!
    for(vector<int>::iterator it=pred[x].begin();it!=pred[x].end();++it)
        if(viz[*it]==0) DF_pred(*it);
}
void init()
{
    for(int i=1;i<=n;i++)
        viz[i]=0;
}
void afisare()
{
    printf("%d\n",nr_comp);
    for(int i=1;i<=nr_comp;i++)
        {
            for(vector<int>::iterator it=sol[i].begin();it!=sol[i].end();++it)
                printf("%d ",*it);
            printf("\n");
        }
}
int main()
{
    freopen("ctc.out","w",stdout);
    citire();
    for(int i=1;i<=n;i++)
        if(viz[i]==0) DF_succ(i);
    init();
    for(;n;n--)
        if(viz[n]==0)
            {
                nr_comp++;
                DF_pred(st[n]);//!!!
            }
    afisare();
    return 0;
}