#include <bits/stdc++.h>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
const int nmax=100005;
int nr_comp,i,x,y,n,m,j,siz_comp;
stack <int> stiv;
vector <int> a[nmax]; /// graf normal
vector <int> b[nmax]; /// graf transpus
vector <int> ras[nmax];
bool viz[nmax],viz2[nmax],incomp[nmax];

void dfs_normal (int nod)
{
    int h,vecini;
    viz[nod]=1;
    vecini=a[nod].size();
    for (h=0;h<vecini;h++)
    {
        if (viz[a[nod][h]]==0)
            dfs_normal(a[nod][h]);
    }

    stiv.push(nod);
}

void dfs_transpus (int nod)
{
    int h,vecini;
    viz2[nod]=1;
    incomp[nod]=1;
    vecini=b[nod].size();
    for (h=0;h<vecini;h++)
    {
        if (viz2[b[nod][h]]==0)
            dfs_transpus(b[nod][h]);
    }

    ras[nr_comp].push_back(nod);
}

int main()
{
    f>>n>>m;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        a[x].push_back(y);
        b[y].push_back(x);
    }

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

    while (!stiv.empty())
    {
        if (incomp[stiv.top()]==0)
        {
            nr_comp++;
            dfs_transpus(stiv.top());
        }
        stiv.pop();
    }

    g<<nr_comp<<'\n';

    for (i=1;i<=nr_comp;i++)
    {
         siz_comp=ras[i].size();
         for (j=0;j<siz_comp;j++)
            g<<ras[i][j]<<" ";
         g<<'\n';
    }
    return 0;
}