#include <fstream>
#include <vector>
#define nmax 100001

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n,m,viz[nmax],vf,st[nmax],j,v[nmax],c;
vector <int> ma[nmax],mat[nmax],rez[nmax];
void citire()
{
    int i,a,b;
    fin>>n>>m;
    for(i=1;i<=m;i++)
    {
        fin>>a>>b;
        ma[a].push_back(b);
        mat[b].push_back(a);
    }
}
void dfs(int x,int op)
{
    viz[x]=1;
    unsigned int i;
    if(op==1)
    {
        for(i=0;i<ma[x].size();i++)
            if(viz[ma[x][i]]==0)
                dfs(ma[x][i],op);
        v[++j]=x;
    }
    else
    {
        for(i=0;i<mat[x].size();i++)
            if(viz[mat[x][i]]==0)
                dfs(mat[x][i],op);
        rez[c].push_back(x);
    }
}
void afisare()
{
    int i,j;
    fout<<c<<'\n';
    for(i=1;i<=c;i++)
    {
        for(j=0;j<rez[i].size();j++)
            fout<<rez[i][j]<<' ';
        fout<<'\n';
    }
}
int main()
{
    int i;
    citire();
    for(i=1;i<=n;i++)
        if(viz[i]==0)
            dfs(i,1);
    for(i=1;i<=n;i++)
        viz[i]=0;
    for(i=n;i>0;i--)
        if(viz[v[i]]==0)
        {
            c++;
            dfs(v[i],2);
        }
    afisare();
    fout.close();
    return 0;
}