#include<cstdio>
#include<vector>
#include<iterator>
#define NMAX 100000+5
using namespace std;
vector<int> V[NMAX];
vector<int> Vt[NMAX];
vector<int> postordine;
vector<int> ctc[NMAX];
int N,M,a,b,c,cnt;
bool viz[NMAX];
void dfs(int x)
{
    vector<int>::iterator it;
    viz[x]=1;
    for(it=V[x].begin(); it!=V[x].end(); it++)
        if(!viz[*it]) dfs(*it);
    postordine.push_back(x);
}
void dfst(int x)
{
    vector<int>::iterator it;
    viz[x]=0;
    ctc[cnt].push_back(x);
    for(it=Vt[x].begin(); it!=Vt[x].end(); it++)
        if(viz[*it]) dfst(*it);
}
void afisare(int x)
{
    vector<int>::iterator it;
    for(it=ctc[x].begin();it!=ctc[x].end();it++)
        printf("%d ",*it);
    printf("\n");
}
int main()
{
    int i;
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    scanf("%d%d",&N,&M);
    for(; M; --M)
    {
        scanf("%d%d",&a,&b);
        V[a].push_back(b);
        Vt[b].push_back(a);
    }
    for(i=1; i<=N; i++)
        if(!viz[i]) dfs(i);
    vector<int>::reverse_iterator it;
    for(it=postordine.rbegin();it!=postordine.rend();it++)
    {
        if(!viz[*it]) continue;
        cnt++;
        dfst(*it);
    }
    printf("%d\n",cnt);
    for(i=1;i<=cnt;i++)
        afisare(i);
    return 0;
}