#include<cstdio>
#define N_MAX 100000
using namespace std;

struct nod
{
    int val;
    nod *next;
};

nod *List[N_MAX+1], *L[N_MAX+1], *ctc[N_MAX+1];
bool viz[N_MAX+1];
int st[N_MAX], vf, n, m, nrc;

inline void Insert(int x, int y)
{
    nod *elem = new nod;
    elem->val = y;
    elem->next = List[x];
    List[x] = elem;
}

inline void InsertReverseGraph(int x, int y)
{
    nod *elem = new nod;
    elem->val = y;
    elem->next = L[x];
    L[x] = elem;
}

void Read()
{
    int i, x, y;
    FILE *fin = fopen("ctc.in","r");
    fscanf(fin,"%d%d",&n,&m);
    for(i=1; i<=m; i++)
    {
        fscanf(fin,"%d%d",&x,&y);
        Insert(x,y);
        InsertReverseGraph(y,x);
    }
    fclose(fin);
}

void DFS(int x)
{
    viz[x] = true;
    nod *p = List[x];
    while(p != NULL)
    {
        if(!viz[p->val])
            DFS(p->val);
        p = p->next;
    }
    st[vf++] = x;
}

void DFSReverseGraph(int x)
{
    viz[x] = true;
    nod *elem = new nod;
    elem->val = x;
    elem->next = ctc[nrc];
    ctc[nrc] = elem;
    nod *p = L[x];
    while(p != NULL)
    {
        if(!viz[p->val])
            DFSReverseGraph(p->val);
        p = p->next;
    }
}

int main()
{
    int i;
    nod *l;
    FILE *fout = fopen("ctc.out","w");
    Read();
    for(i=1; i<=n; i++)
        if(!viz[i])
            DFS(i);
    for(i=1; i<=n; i++)
        viz[i] = false;
    while(vf > 0)
    {
        vf--;
        if(!viz[st[vf]])
        {
            nrc++;
            DFSReverseGraph(st[vf]);
        }
    }
    fprintf(fout,"%d\n",nrc);
    for(i=1; i<=nrc; i++)
    {
        l = ctc[i];
        while(l != NULL)
        {
            fprintf(fout,"%d ",l->val);
            l = l->next;
        }
        fprintf(fout,"\n");
    }
    fclose(fout);
    return 0;
}