#include <bits/stdc++.h>
using namespace std;
vector <int> v[50005];
vector <int> vt[50005];
vector <int> tare[50005];
int n,m,i,comp,nr,vect[50005],viz[50005],x,y,j;
struct andreea
{
    int poz, unu;
}ras[50005];
bool cmp(andreea a, andreea b)
{
    if(a.unu>=b.unu)return 0;
    return 1;
}
void dfs(int nod)
{
    int i;
    viz[nod]=1;
    for(i=0;i<v[nod].size();i++)
        if(viz[v[nod][i]]==0)dfs(v[nod][i]);
    nr++;
    vect[nr]=nod;
}
void dfp(int nod)
{
    int i;
    viz[nod]=2;
    tare[comp].push_back(nod);
    for(i=0;i<vt[nod].size();i++)
        if(viz[vt[nod][i]]==1)dfp(vt[nod][i]);
}
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);
        vt[y].push_back(x);
    }
    for(i=1;i<=n;i++)
    {
        if(viz[i]==0)
        {
            dfs(i);
        }
    }
    for(i=nr;i>=1;i--)
    {
        if(viz[vect[i]]==1)
        {
            comp++;
            dfp(vect[i]);
        }
    }
    printf("%d",comp);
    for(i=1;i<=comp;i++)
    {
        ras[i].poz=i;
        ras[i].unu=n+2;
        for(j=0;j<tare[i].size();j++)
            if(ras[i].unu>tare[i][j])ras[i].unu=tare[i][j];
    }
    sort(ras+1,ras+comp+1,cmp);
    for(i=1;i<=comp;i++)
    {
        printf("\n");
       // printf("\n%d ",tare[ras[i].poz].size());
        sort(tare[i].begin(),tare[i].end());
        for(j=0;j<tare[ras[i].poz].size();j++)
            printf("%d ",tare[ras[i].poz][j]);
    }
    return 0;
}