#include <bits/stdc++.h>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
vector <int> v[100009], ctc[100009], vt[100009];
int curr=0;
bool viz[100009];
int lin[100009], cnt=0;
void dfs0 (int nod)
{
    viz[nod]=1;
    for(auto y:v[nod])
    {
        if (!viz[y])
            dfs0(y);
    }
    lin[++cnt]=nod;
}
void dfs (int nod)
{
    ctc[curr].push_back(nod);
    viz[nod]=1;
    for (auto y:vt[nod])
        if (!viz[y]) dfs(y);
}
signed main ()
{
    int n, m;
    f >> n >> m;
    for (int i=1; i<=m; i++)
    {
        int x, y;
        f >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    for (int i=1; i<=n; i++)
    {
        if (!viz[i])
            dfs0 (i);
    }
    for (int i=1; i<=n; i++)
        viz[i]=0;
    for (int i=n; i>=1; i--)
    {
        if (!viz[lin[i]])
            curr++, dfs (lin[i]);
    }
    g<<curr << '\n';
    for (int i=1; i<=curr; i++)
    {
        for (auto y:ctc[i])
            g << y <<' ';
        g <<'\n';
    }
}