#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
vector<int>v[100001];
vector<int>v1[100001];
int valid[100001];
vector<int>sol[100001];
struct graf
{
    int nr,e;
}viz[100001];
int n,i,x,y,m,t,nrcmp;
int cmp(graf r,graf p)
{
    if (r.e<p.e) return 0;
    return 1;
}
void DF(int nod)
{
    ++t;
    viz[nod].e=1;
    vector<int>::iterator it;
    for(it=v[nod].begin();it!=v[nod].end();++it)
    {
        if (viz[*it].e==0) DF(*it);
    }
    ++t;
    viz[nod].e=t;
}
void DF1(int nod)
{
    sol[nrcmp].push_back(nod);
    valid[nod]=nrcmp;
    vector<int>::iterator it;
    for (it=v1[nod].begin();it!=v1[nod].end();++it)
    {
        if (valid[*it]==0) DF1(*it);
    }
}
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);
        v1[y].push_back(x);
    }
    t=0;
    for (i=1;i<=n;++i)
    {
        viz[i].nr=i;
        if (viz[i].e==0)
        {
            DF(i);
        }
    }
    sort(viz+1,viz+n+1,cmp);
    nrcmp=0;
    for (i=1;i<=n;++i)
    {
        if (valid[viz[i].nr]==0)
        {
            ++nrcmp;
            DF1(viz[i].nr);
        }
    }
    printf("%d\n",nrcmp);
    for (i=1;i<=nrcmp;++i)
    {
        vector<int>::iterator it;
        for (it=sol[i].begin();it!=sol[i].end();++it)
            printf("%d ",*it);
        printf("\n");
    }
    return 0;
}