//g     = graful
//gt    = graful transpus
//dfs pe g
//dfst pe gt
//ctc   = structura in care se afla componentele tare conexe
 
#include <stdio.h>
#include <string.h>
#include <vector>
 
#define maxN 131072
 
using namespace std;
 
int use[maxN];
int st[maxN];
 
vector <int> g[maxN];
vector <int> gt[maxN];
vector <int> ctc[maxN];
 
int sol=0;
 
inline void dfs(int nod)
{
        use[nod]=1;
        for(int i=0;i<g[nod].size();++i)
                if(!use[g[nod][i]]) dfs(g[nod][i]);
 
        st[++st[0]]=nod;
}
 
inline void dfst(int nod)
{
        use[nod]=1;
        for(int i=0;i<gt[nod].size();++i)
                if(!use[gt[nod][i]]) dfst(gt[nod][i]);
 
        ctc[sol].push_back(nod);
}
 
int main(int argc,char *argv[])
{
        int M,N,x,y;
 
        freopen("ctc.in","r",stdin);
        freopen("ctc.out","w",stdout);
 
        scanf("%d%d",&N,&M);
 
        for(int i=1;i<=M;++i)
        {
                scanf("%d%d",&x,&y);
                g[x].push_back(y);
                gt[y].push_back(x);
        }
 
        memset(st,0,sizeof(st));
        memset(use,0,sizeof(use));
 
        for(int i=1;i<=N;++i)
                if(!use[i]) dfs(i);
 
        memset(use,0,sizeof(use));
 
        for(int i=N;i>0;--i)
                if(!use[st[i]])
        {
                ++sol;
                dfst(st[i]);
        }
 
        printf("%d\n",sol);
        for(int i=1;i<=sol;++i)
        {
                for(int j=0;j<ctc[i].size();++j)
                        printf("%d ",ctc[i][j]);
                printf("\n");
        }
 
        return 0;
}