#include <fstream>
#include <vector>
#include <stack>
using namespace std;
const int NMAX = 100005;

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

vector <int> g[NMAX],gt[NMAX], sol[NMAX];
stack  <int> st;

int viz1[NMAX], viz[NMAX], n,m;
int  nr_comp;;

void cit()
{
    int x,y;
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
        fin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
}

void timpi(int x)
{
    int y;
    viz[x]=1;
    for( unsigned int i=0;i<g[x].size();++i)
    {
        y=g[x][i];
        if(viz[y]==0)
            timpi(y);
    }
    st.push(x);
}

void dfs(int x)
{
    int y;
    viz1[x]=1;
    sol[nr_comp].push_back(x);
    for(unsigned int i=0;i<gt[x].size();++i)
        {
            y = gt[x][i];
            if(viz1[y]==0)
                dfs(y);
        }
}

void afis()
{
    fout<<nr_comp<<'\n';
    for(int i=1;i<=nr_comp;++i)
    {
        for(unsigned int j=0;j<sol[i].size();++j)
            fout<< sol[i][j]<<" ";
        fout<<'\n';
    }
}
int main()
{
    int x;
    cit();

    for(int i=1;i<=n;i++)
        if(viz[i]==0)
           timpi(i);

    while(!st.empty())
    {
        x=st.top();
        st.pop();
        if(viz1[x]==0){
            nr_comp++;
            dfs(x);
        }
    }

    afis();



    return 0;
}