#include <cstdio>
#include <vector>
#define DIM 10000
using namespace std;
char buff[DIM];
int poz=0;
void citeste(int &numar)
{
     numar = 0;
     while (buff[poz] < '0' || buff[poz] > '9')
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM)
               fread(buff,1,DIM,stdin),poz=0;
     }
}
vector<int>adj[100023],sol[100023],stiva;
bool vis[100023],ins[100023];
int niv[100023],low[100023];
int n,m,comp,ind;
void tarjan(int nod)
{
    vis[nod]=1;
    niv[nod]=++ind;
    low[nod]=niv[nod];
    stiva.push_back(nod);
    ins[nod]=1;
    vector<int>::iterator it;
    for(it=adj[nod].begin();it!=adj[nod].end();++it)
    {
        if(vis[*it]==0) tarjan(*it);
        if(ins[*it]==1&&low[nod]>low[*it]) low[nod]=low[*it];
    }
    if(niv[nod]==low[nod])
    {
        ++comp;
        while(1)
        {
            int vcn=stiva.back();
            ins[vcn]=0;
            sol[comp].push_back(vcn);
            stiva.pop_back();
            if(vcn==nod) break;
        }
    }
}
int main()
{
    freopen ("ctc.in","r",stdin);
    freopen ("ctc.out","w",stdout);
    int x1,x2;
    citeste(n),citeste(m);
    for(int i=1;i<=m;i++)
    {
        citeste(x1),citeste(x2);
        adj[x1].push_back(x2);
    }
    for(int i=1;i<=n;i++)
    {
        if(vis[i]==0) tarjan(i);
    }
    printf("%d\n",comp);
    for(int i=1;i<=comp;i++)
    {
        vector<int>::iterator it;
        for(it=sol[i].begin();it!=sol[i].end();++it) printf("%d ",*it);
        printf("\n");
    }
}