#include <cstdio>
#include <algorithm>
#include <vector>

using namespace std;

vector<int>v[100010],sol[100010];
vector<int>::iterator it;
int stiva[100010],vaz[100010],mincomp[100010],n,m,i,x,y,nr,nrsol;
char instiva[100010];

void dfs(int nod)
{
    vector<int>::iterator it;
    vaz[nod]=mincomp[nod]=++nr;
    stiva[++stiva[0]]=nod;
    instiva[nod]=1;
    for(it=v[nod].begin();it!=v[nod].end();it++)
        if(!vaz[*it])
        {
            dfs(*it);
            mincomp[nod]=min(mincomp[nod],mincomp[*it]);
        }
        else if(instiva[*it]) mincomp[nod]=min(mincomp[nod],mincomp[*it]);
    if(vaz[nod]==mincomp[nod])
    {
        nrsol++;
        x=0;
        do
        {
            x=stiva[stiva[0]--];
            sol[nrsol].push_back(x);
            instiva[x]=0;
        }while(nod!=x);
    }
}

int main()
{
    freopen("ctc.in", "r", stdin);
    freopen("ctc.out", "w", stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        scanf("%d%d",&x,&y);
        v[x].push_back(y);
    }
    for(i=1;i<=n;i++)
        if(!vaz[i]) dfs(i);
    printf("%d\n",nrsol);
    for(i=1;i<=nrsol;i++)
    {
        for(it=sol[i].begin();it!=sol[i].end();it++) printf("%d ",*it);
        printf("\n");
    }
    return 0;
}