#include <cstdio>
#include <bitset>

#define Nmax 100005
#define Bmax 600005
using namespace std;

int G[Nmax],Gt[Nmax],CTC[Nmax],Stak[Nmax];
bitset<Nmax> used;
int DIM,vf,nctc;

class node{
public:
    int inf,next;
    node(){}
    node(int elem,int to){
        inf = elem;
        next = to;
    }
};
node Buff[Bmax];

void Add_list(int &head,int val){
    Buff[++DIM] = node(val,head);
    head = DIM;
}


int N,M;
void Read()
{
    scanf("%d%d",&N,&M);
    int a,b;
    for(int i = 1; i <= M; ++i)
    {
        scanf("%d%d",&a,&b);
        Add_list(G[a],b);
        Add_list(Gt[b],a);
    }
}

void DFS(int k)
{
    used[k] = 1;
    for(int v = G[k]; v; v = Buff[v].next)
        if(!used[Buff[v].inf])
            DFS(Buff[v].inf);

    Stak[++vf] = k;
}

void DFST(int k)
{
    Add_list(CTC[nctc],k);
    used[k] = 1;
    for(int v = Gt[k]; v; v = Buff[v].next)
        if(!used[Buff[v].inf])
            DFST(Buff[v].inf);


}

void Kosaraju()
{
    for(int i = 1; i <= N; ++i)
        if(!used[i])
            DFS(i);
    used = 0;
    while(vf > 0)
    {
        while(vf > 0 && used[ Stak[vf] ])
            --vf;
        if(vf == 0)
            continue;
        ++nctc;
        DFST(Stak[vf]);
    }
}

void Print()
{
    printf("%d\n",nctc);
    for(int i = 1; i <= nctc; ++i)
    {
        for(int v = CTC[i]; v; v = Buff[v].next)
            printf("%d ",Buff[v].inf);
        printf("\n");
    }
}

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

    Read();
    Kosaraju();
    Print();

    return 0;
}