#include <cstdio>
#include <queue>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
#define MAX 100001

vector<int>g[MAX];
vector<int>t[MAX];

queue<int>q;
queue<queue<int> >d;
bool viz[MAX],l[MAX],r[MAX];
int n;

void dfs1(int x){
    int y;
    l[x]=1;
    for(int i=0;i<g[x].size();i++)
    {
        y=g[x][i];
        if(!l[y] && !viz[y])dfs1(y);
    }
}

void dfs2(int x){
    int y;
    r[x]=1;
    for(int i=0;i<t[x].size();i++)
    {
        y=t[x][i];
        if(!r[y] && !viz[y])dfs2(y);
    }
}

int main(){
    int m,x,y;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
        scanf("%d %d",&n,&m);
        while(m--)
        {
            scanf("%d %d",&x,&y);
            g[x].push_back(y);
            t[y].push_back(x);
        }
    for(int i=1;i<=n;i++)
    if(viz[i]==0)
    {
        memset(l,0,sizeof(l));
        memset(r,0,sizeof(r));
        dfs1(i);
        dfs2(i);
        for(int j=1;j<=n;j++)
        if(l[j] && r[j])
        {
            q.push(j);
            viz[j]=1;
        }
        if(q.size()>1)d.push(q); else viz[i]=0;
     //   for(int i=1;i<=n;i++)if(viz[i])printf("%d ",i); printf("\n");
     //   printf("%d\n",i);
   //  if(i==4){
   //      for(int i=1;i<=n;i++)printf("%d ",l[i]); printf("\n");
    //     for(int i=1;i<=n;i++)printf("%d ",r[i]); printf("\n");
     //}
        while(q.size()>0)q.pop();
    }
    printf("%d\n",d.size());
    while(d.size()>0)
    {
        while(d.front().size()>0)
        {
            printf("%d ",d.front().front());
            d.front().pop();
        }
        printf("\n");
        d.pop();
    }
    return 0;
}