#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#define N 100005
#define min(a,b) a<b?a:b

///algoritmul lui tarjan

using namespace std;

int vizitat[N];
int n,m,a,b,nr;
vector <int> graf[N],ceva,sol[N];
stack <int> stiva;
int index[N],lowlink[N],indice;

void citire()
{
    scanf("%d %d\n", &n, &m);
    for(int i=0;i<m;i++)
        {
            scanf("%d %d\n", &a, &b);
            graf[a].push_back(b);
        }
}

void dfs(int x)
{
    index[x]=++indice;
    lowlink[x]=indice;
    stiva.push(x);
    vizitat[x]=1;
    for(int i=0;i<graf[x].size();i++)
    {
        int nod=graf[x][i];
        if(!index[nod])
        {
            dfs(nod);
            lowlink[x]=min(lowlink[x],lowlink[nod]);

        }
        else
            if(vizitat[nod])
                lowlink[x]=min(lowlink[x],index[nod]);
    }
    if(index[x]==lowlink[x])
        {
            nr++;
            int y;
            while(x!=y)
            {
                y=stiva.top();
                sol[nr].push_back(y);
                stiva.pop();
                vizitat[y]=0;
            }
        }
}

void tarjan()
{
    for(int i=1;i<=n;i++)
        if(!index[i])
            dfs(i);
}

void afisare()
{
    cout<<nr<<"\n";
    for(int i=1;i<=nr;i++)
    {
        for(int j=0;j<sol[i].size();j++)
            printf("%d ", sol[i][j]);
        printf("\n");
    }

}

int main()
{
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    citire();
    tarjan();
    afisare();
    return 0;
}